81520643600 has 120 divisors (see below), whose sum is σ = 213802080672. Its totient is φ = 29623910400.

The previous prime is 81520643587. The next prime is 81520643639. The reversal of 81520643600 is 634602518.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7575824 + ... + 7586576.

Almost surely, 2^81520643600 is an apocalyptic number.

81520643600 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 81520643600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (106901040336).

81520643600 is an abundant number, since it is smaller than the sum of its proper divisors (132281437072).

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

81520643600 is a wasteful number, since it uses less digits than its factorization.

81520643600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12505 (or 12494 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 35.

The spelling of 81520643600 in words is "eighty-one billion, five hundred twenty million, six hundred forty-three thousand, six hundred".