81497309568 has 128 divisors (see below), whose sum is σ = 219366161280. Its totient is φ = 26804097024.

The previous prime is 81497309549. The next prime is 81497309587. The reversal of 81497309568 is 86590379418.

It is an interprime number because it is at equal distance from previous prime (81497309549) and next prime (81497309587).

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×81497309568² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 40890780 + ... + 40892772.

It is an arithmetic number, because the mean of its divisors is an integer number (1713798135).

Almost surely, 2^81497309568 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81497309568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109683080640).

81497309568 is an abundant number, since it is smaller than the sum of its proper divisors (137868851712).

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

81497309568 is a wasteful number, since it uses less digits than its factorization.

81497309568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3376 (or 3364 counting only the distinct ones).

The product of its (nonzero) digits is 13063680, while the sum is 60.

The spelling of 81497309568 in words is "eighty-one billion, four hundred ninety-seven million, three hundred nine thousand, five hundred sixty-eight".