81371815920 has 480 divisors, whose sum is σ = 298252910592. Its totient is φ = 20577908736.

The previous prime is 81371815901. The next prime is 81371815969. The reversal of 81371815920 is 2951817318.

It is a super-2 number, since 2×81371815920² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 56783524 + ... + 56784956.

Almost surely, 2^81371815920 is an apocalyptic number.

81371815920 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 81371815920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (149126455296).

81371815920 is an abundant number, since it is smaller than the sum of its proper divisors (216881094672).

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

81371815920 is a wasteful number, since it uses less digits than its factorization.

81371815920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1611 (or 1593 counting only the distinct ones).

The product of its (nonzero) digits is 120960, while the sum is 45.

The spelling of 81371815920 in words is "eighty-one billion, three hundred seventy-one million, eight hundred fifteen thousand, nine hundred twenty".