81664157 has 2 divisors, whose sum is σ = 81664158. Its totient is φ = 81664156.

The previous prime is 81664153. The next prime is 81664171. The reversal of 81664157 is 75146618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 47803396 + 33860761 = 6914^2 + 5819^2 .

It is a cyclic number.

It is not a de Polignac number, because 81664157 - 2² = 81664153 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81664157.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81664153) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40832078 + 40832079.

It is an arithmetic number, because the mean of its divisors is an integer number (40832079).

Almost surely, 2^81664157 is an apocalyptic number.

It is an amenable number.

81664157 is a deficient number, since it is larger than the sum of its proper divisors (1).

81664157 is an equidigital number, since it uses as much as digits as its factorization.

81664157 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40320, while the sum is 38.

The square root of 81664157 is about 9036.8222844095. The cubic root of 81664157 is about 433.8542216758.

The spelling of 81664157 in words is "eighty-one million, six hundred sixty-four thousand, one hundred fifty-seven".