81902257 has 2 divisors, whose sum is σ = 81902258. Its totient is φ = 81902256.

The previous prime is 81902251. The next prime is 81902269. The reversal of 81902257 is 75220918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77369616 + 4532641 = 8796^2 + 2129^2 .

It is a cyclic number.

It is not a de Polignac number, because 81902257 - 2⁷ = 81902129 is a prime.

It is not a weakly prime, because it can be changed into another prime (81902251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40951128 + 40951129.

It is an arithmetic number, because the mean of its divisors is an integer number (40951129).

Almost surely, 2^81902257 is an apocalyptic number.

It is an amenable number.

81902257 is a deficient number, since it is larger than the sum of its proper divisors (1).

81902257 is an equidigital number, since it uses as much as digits as its factorization.

81902257 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 81902257 is about 9049.9865745757. The cubic root of 81902257 is about 434.2754609799.

The spelling of 81902257 in words is "eighty-one million, nine hundred two thousand, two hundred fifty-seven".