81988257 has 16 divisors (see below), whose sum is σ = 120234240. Its totient is φ = 49379712.

The previous prime is 81988243. The next prime is 81988303. The reversal of 81988257 is 75288918.

It is not a de Polignac number, because 81988257 - 2⁷ = 81988129 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81988237) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20532 + ... + 24197.

It is an arithmetic number, because the mean of its divisors is an integer number (7514640).

Almost surely, 2^81988257 is an apocalyptic number.

It is an amenable number.

81988257 is a deficient number, since it is larger than the sum of its proper divisors (38245983).

81988257 is a wasteful number, since it uses less digits than its factorization.

81988257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44792.

The product of its digits is 322560, while the sum is 48.

The square root of 81988257 is about 9054.7367162165. The cubic root of 81988257 is about 434.4274088689.

The spelling of 81988257 in words is "eighty-one million, nine hundred eighty-eight thousand, two hundred fifty-seven".