81637657 has 2 divisors, whose sum is σ = 81637658. Its totient is φ = 81637656.

The previous prime is 81637631. The next prime is 81637669. The reversal of 81637657 is 75673618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72999936 + 8637721 = 8544^2 + 2939^2 .

It is a cyclic number.

It is not a de Polignac number, because 81637657 - 2¹⁵ = 81604889 is a prime.

It is equal to p_4759549 and since 81637657 and 4759549 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81637687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40818828 + 40818829.

It is an arithmetic number, because the mean of its divisors is an integer number (40818829).

Almost surely, 2^81637657 is an apocalyptic number.

It is an amenable number.

81637657 is a deficient number, since it is larger than the sum of its proper divisors (1).

81637657 is an equidigital number, since it uses as much as digits as its factorization.

81637657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 211680, while the sum is 43.

The square root of 81637657 is about 9035.3559420756. The cubic root of 81637657 is about 433.8072880673.

The spelling of 81637657 in words is "eighty-one million, six hundred thirty-seven thousand, six hundred fifty-seven".