81378198720 has 560 divisors, whose sum is σ = 356289181248. Its totient is φ = 17169408000.

The previous prime is 81378198703. The next prime is 81378198721. The reversal of 81378198720 is 2789187318.

It is a happy number.

81378198720 is a `hidden beast` number, since 81 + 378 + 198 + 7 + 2 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (560).

It is a super-2 number, since 2×81378198720² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (81378198721) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 2341470 + ... + 2375970.

Almost surely, 2^81378198720 is an apocalyptic number.

81378198720 is a gapful number since it is divisible by the number (80) 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 81378198720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (178144590624).

81378198720 is an abundant number, since it is smaller than the sum of its proper divisors (274910982528).

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

81378198720 is a wasteful number, since it uses less digits than its factorization.

81378198720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34550 (or 34531 counting only the distinct ones).

The product of its (nonzero) digits is 1354752, while the sum is 54.

The spelling of 81378198720 in words is "eighty-one billion, three hundred seventy-eight million, one hundred ninety-eight thousand, seven hundred twenty".