81902251 has 2 divisors, whose sum is σ = 81902252. Its totient is φ = 81902250.

The previous prime is 81902239. The next prime is 81902257. The reversal of 81902251 is 15220918.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81902251 - 2⁹ = 81901739 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81902257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40951125 + 40951126.

It is an arithmetic number, because the mean of its divisors is an integer number (40951126).

Almost surely, 2^81902251 is an apocalyptic number.

81902251 is a deficient number, since it is larger than the sum of its proper divisors (1).

81902251 is an equidigital number, since it uses as much as digits as its factorization.

81902251 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 81902251 is about 9049.9862430835. The cubic root of 81902251 is about 434.2754503751.

The spelling of 81902251 in words is "eighty-one million, nine hundred two thousand, two hundred fifty-one".