81708656400 has 540 divisors, whose sum is σ = 347220447600. Its totient is φ = 17692577280.

The previous prime is 81708656363. The next prime is 81708656461. The reversal of 81708656400 is 465680718.

It is a happy number.

81708656400 is a `hidden beast` number, since 8 + 1 + 7 + 0 + 86 + 564 + 0 + 0 = 666.

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

It is an unprimeable number.

It is a polite number, since it can be written in 107 ways as a sum of consecutive naturals, for example, 3339411 + ... + 3363789.

Almost surely, 2^81708656400 is an apocalyptic number.

81708656400 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 81708656400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (173610223800).

81708656400 is an abundant number, since it is smaller than the sum of its proper divisors (265511791200).

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

81708656400 is a wasteful number, since it uses less digits than its factorization.

81708656400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24436 (or 24415 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 45.

The spelling of 81708656400 in words is "eighty-one billion, seven hundred eight million, six hundred fifty-six thousand, four hundred".