81749791 has 2 divisors, whose sum is σ = 81749792. Its totient is φ = 81749790.

The previous prime is 81749783. The next prime is 81749807. The reversal of 81749791 is 19794718.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81749791 - 2³ = 81749783 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81749491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40874895 + 40874896.

It is an arithmetic number, because the mean of its divisors is an integer number (40874896).

Almost surely, 2^81749791 is an apocalyptic number.

81749791 is a deficient number, since it is larger than the sum of its proper divisors (1).

81749791 is an equidigital number, since it uses as much as digits as its factorization.

81749791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 127008, while the sum is 46.

The square root of 81749791 is about 9041.5591022788. The cubic root of 81749791 is about 434.0058169211.

The spelling of 81749791 in words is "eighty-one million, seven hundred forty-nine thousand, seven hundred ninety-one".