81940257 has 12 divisors (see below), whose sum is σ = 135266560. Its totient is φ = 46822968.

The previous prime is 81940249. The next prime is 81940259. The reversal of 81940257 is 75204918.

It is not a de Polignac number, because 81940257 - 2³ = 81940249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81940259) 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, 650257 + ... + 650382.

Almost surely, 2^81940257 is an apocalyptic number.

It is an amenable number.

81940257 is a deficient number, since it is larger than the sum of its proper divisors (53326303).

81940257 is a wasteful number, since it uses less digits than its factorization.

81940257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1300652 (or 1300649 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 81940257 is about 9052.0857817411. The cubic root of 81940257 is about 434.3426138544.

The spelling of 81940257 in words is "eighty-one million, nine hundred forty thousand, two hundred fifty-seven".