81394728920064 has 1320 divisors, whose sum is σ = 315137639028960. Its totient is φ = 20735341756416.

The previous prime is 81394728920027. The next prime is 81394728920101. The reversal of 81394728920064 is 46002982749318.

81394728920064 is a `hidden beast` number, since 8 + 1 + 3 + 9 + 472 + 89 + 20 + 0 + 64 = 666.

It is an interprime number because it is at equal distance from previous prime (81394728920027) and next prime (81394728920101).

It is a super-3 number, since 3×81394728920064³ (a number of 43 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a junction number, because it is equal to n+sod(n) for n = 81394728919983 and 81394728920010.

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 1312723687 + ... + 1312785689.

It is an arithmetic number, because the mean of its divisors is an integer number (238740635628).

Almost surely, 2^{81394728920064} is an apocalyptic number.

81394728920064 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81394728920064, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (157568819514480).

81394728920064 is an abundant number, since it is smaller than the sum of its proper divisors (233742910108896).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81394728920064 is a wasteful number, since it uses less digits than its factorization.

81394728920064 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62085 (or 62051 counting only the distinct ones).

The product of its (nonzero) digits is 41803776, while the sum is 63.

The spelling of 81394728920064 in words is "eighty-one trillion, three hundred ninety-four billion, seven hundred twenty-eight million, nine hundred twenty thousand, sixty-four".