81644525907 has 16 divisors (see below), whose sum is σ = 131728983552. Its totient is φ = 43909660800.

The previous prime is 81644525881. The next prime is 81644525917. The reversal of 81644525907 is 70952544618.

It is not a de Polignac number, because 81644525907 - 2¹⁶ = 81644460371 is a prime.

It is a super-2 number, since 2×81644525907² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a self number, because there is not a number n which added to its sum of digits gives 81644525907.

It is not an unprimeable number, because it can be changed into a prime (81644525917) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 114347719 + ... + 114348432.

It is an arithmetic number, because the mean of its divisors is an integer number (8233061472).

Almost surely, 2^81644525907 is an apocalyptic number.

81644525907 is a deficient number, since it is larger than the sum of its proper divisors (50084457645).

81644525907 is a wasteful number, since it uses less digits than its factorization.

81644525907 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 228696178.

The product of its (nonzero) digits is 2419200, while the sum is 51.

The spelling of 81644525907 in words is "eighty-one billion, six hundred forty-four million, five hundred twenty-five thousand, nine hundred seven".