81400921056 has 384 divisors, whose sum is σ = 293236070400. Its totient is φ = 21392916480.

The previous prime is 81400921039. The next prime is 81400921127. The reversal of 81400921056 is 65012900418.

It is a super-2 number, since 2×81400921056² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 81400921056.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 24450400 + ... + 24453728.

It is an arithmetic number, because the mean of its divisors is an integer number (763635600).

Almost surely, 2^81400921056 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 81400921056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (146618035200).

81400921056 is an abundant number, since it is smaller than the sum of its proper divisors (211835149344).

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

81400921056 is a wasteful number, since it uses less digits than its factorization.

81400921056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3679 (or 3665 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The spelling of 81400921056 in words is "eighty-one billion, four hundred million, nine hundred twenty-one thousand, fifty-six".