81892991 has 2 divisors, whose sum is σ = 81892992. Its totient is φ = 81892990.

The previous prime is 81892973. The next prime is 81892997. The reversal of 81892991 is 19929818.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81892991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81892997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40946495 + 40946496.

It is an arithmetic number, because the mean of its divisors is an integer number (40946496).

Almost surely, 2^81892991 is an apocalyptic number.

81892991 is a deficient number, since it is larger than the sum of its proper divisors (1).

81892991 is an equidigital number, since it uses as much as digits as its factorization.

81892991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 93312, while the sum is 47.

The square root of 81892991 is about 9049.4746256344. The cubic root of 81892991 is about 434.2590831317.

The spelling of 81892991 in words is "eighty-one million, eight hundred ninety-two thousand, nine hundred ninety-one".