81974751 has 4 divisors (see below), whose sum is σ = 109299672. Its totient is φ = 54649832.

The previous prime is 81974741. The next prime is 81974771. The reversal of 81974751 is 15747918.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81974751 - 2⁶ = 81974687 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81974741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13662456 + ... + 13662461.

It is an arithmetic number, because the mean of its divisors is an integer number (27324918).

Almost surely, 2^81974751 is an apocalyptic number.

81974751 is a deficient number, since it is larger than the sum of its proper divisors (27324921).

81974751 is a wasteful number, since it uses less digits than its factorization.

81974751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27324920.

The product of its digits is 70560, while the sum is 42.

The square root of 81974751 is about 9053.9908880007. The cubic root of 81974751 is about 434.4035530184.

The spelling of 81974751 in words is "eighty-one million, nine hundred seventy-four thousand, seven hundred fifty-one".