81373257 has 48 divisors (see below), whose sum is σ = 142629760. Its totient is φ = 43670016.

The previous prime is 81373247. The next prime is 81373261. The reversal of 81373257 is 75237318.

It is not a de Polignac number, because 81373257 - 2¹¹ = 81371209 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81373247) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 187713 + ... + 188145.

Almost surely, 2^81373257 is an apocalyptic number.

It is an amenable number.

81373257 is a deficient number, since it is larger than the sum of its proper divisors (61256503).

81373257 is a wasteful number, since it uses less digits than its factorization.

81373257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 622 (or 619 counting only the distinct ones).

The product of its digits is 35280, while the sum is 36.

The square root of 81373257 is about 9020.7126658596. The cubic root of 81373257 is about 433.3384574673.

The spelling of 81373257 in words is "eighty-one million, three hundred seventy-three thousand, two hundred fifty-seven".