81562391 has 2 divisors, whose sum is σ = 81562392. Its totient is φ = 81562390.

The previous prime is 81562381. The next prime is 81562409. The reversal of 81562391 is 19326518.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81562391 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81562381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40781195 + 40781196.

It is an arithmetic number, because the mean of its divisors is an integer number (40781196).

Almost surely, 2^81562391 is an apocalyptic number.

81562391 is a deficient number, since it is larger than the sum of its proper divisors (1).

81562391 is an equidigital number, since it uses as much as digits as its factorization.

81562391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 35.

The square root of 81562391 is about 9031.1898994540. The cubic root of 81562391 is about 433.6739305789.

The spelling of 81562391 in words is "eighty-one million, five hundred sixty-two thousand, three hundred ninety-one".