81257644 has 12 divisors (see below), whose sum is σ = 153139504. Its totient is φ = 37503504.

The previous prime is 81257641. The next prime is 81257651. The reversal of 81257644 is 44675218.

It is a hoax number, since the sum of its digits (37) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (81257641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 781272 + ... + 781375.

Almost surely, 2^81257644 is an apocalyptic number.

It is an amenable number.

81257644 is a deficient number, since it is larger than the sum of its proper divisors (71881860).

81257644 is a wasteful number, since it uses less digits than its factorization.

81257644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1562664 (or 1562662 counting only the distinct ones).

The product of its digits is 53760, while the sum is 37.

The square root of 81257644 is about 9014.3021915177. The cubic root of 81257644 is about 433.1331348737.

The spelling of 81257644 in words is "eighty-one million, two hundred fifty-seven thousand, six hundred forty-four".