81521825643 has 12 divisors (see below), whose sum is σ = 117777567648. Its totient is φ = 54336890160.

The previous prime is 81521825639. The next prime is 81521825677. The reversal of 81521825643 is 34652812518.

81521825643 is a `hidden beast` number, since 8 + 1 + 5 + 2 + 1 + 82 + 564 + 3 = 666.

It is not a de Polignac number, because 81521825643 - 2² = 81521825639 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81521825683) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 869043 + ... + 958268.

It is an arithmetic number, because the mean of its divisors is an integer number (9814797304).

Almost surely, 2^81521825643 is an apocalyptic number.

81521825643 is a deficient number, since it is larger than the sum of its proper divisors (36255742005).

81521825643 is a wasteful number, since it uses less digits than its factorization.

81521825643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1832274 (or 1832271 counting only the distinct ones).

The product of its digits is 460800, while the sum is 45.

The spelling of 81521825643 in words is "eighty-one billion, five hundred twenty-one million, eight hundred twenty-five thousand, six hundred forty-three".