81521670400 has 243 divisors, whose sum is σ = 209099441649. Its totient is φ = 31466588160.

The previous prime is 81521670379. The next prime is 81521670421. The reversal of 81521670400 is 407612518.

The square root of 81521670400 is 285520.

It is a perfect power (a square), and thus also a powerful number.

It is an interprime number because it is at equal distance from previous prime (81521670379) and next prime (81521670421).

It can be written as a sum of positive squares in only one way, i.e., 29347801344 + 52173869056 = 171312^2 + 228416^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 982188759 + ... + 982188841.

Almost surely, 2^81521670400 is an apocalyptic number.

81521670400 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

81521670400 is the 285520-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81521670400

81521670400 is an abundant number, since it is smaller than the sum of its proper divisors (127577771249).

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

81521670400 is an frugal number, since it uses more digits than its factorization.

81521670400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 278 (or 133 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 34.

The spelling of 81521670400 in words is "eighty-one billion, five hundred twenty-one million, six hundred seventy thousand, four hundred".