81637669 has 2 divisors, whose sum is σ = 81637670. Its totient is φ = 81637668.

The previous prime is 81637657. The next prime is 81637681. The reversal of 81637669 is 96673618.

It is a balanced prime because it is at equal distance from previous prime (81637657) and next prime (81637681).

It can be written as a sum of positive squares in only one way, i.e., 53949025 + 27688644 = 7345^2 + 5262^2 .

It is a cyclic number.

It is not a de Polignac number, because 81637669 - 2²³ = 73249061 is a prime.

It is a super-2 number, since 2×81637669² = 13329417999507122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81637609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40818834 + 40818835.

It is an arithmetic number, because the mean of its divisors is an integer number (40818835).

Almost surely, 2^81637669 is an apocalyptic number.

It is an amenable number.

81637669 is a deficient number, since it is larger than the sum of its proper divisors (1).

81637669 is an equidigital number, since it uses as much as digits as its factorization.

81637669 is an evil number, because the sum of its binary digits is even.

The product of its digits is 326592, while the sum is 46.

The square root of 81637669 is about 9035.3566061335. The cubic root of 81637669 is about 433.8073093226.

The spelling of 81637669 in words is "eighty-one million, six hundred thirty-seven thousand, six hundred sixty-nine".