991725931 has 4 divisors (see below), whose sum is σ = 1133401072. Its totient is φ = 850050792.

The previous prime is 991725913. The next prime is 991725967. The reversal of 991725931 is 139527199.

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 991725931 - 2⁹ = 991725419 is a prime.

It is a super-2 number, since 2×991725931² = 1967040644435633522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991725901) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 70837560 + ... + 70837573.

It is an arithmetic number, because the mean of its divisors is an integer number (283350268).

Almost surely, 2^991725931 is an apocalyptic number.

991725931 is a deficient number, since it is larger than the sum of its proper divisors (141675141).

991725931 is a wasteful number, since it uses less digits than its factorization.

991725931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141675140.

The product of its digits is 153090, while the sum is 46.

The square root of 991725931 is about 31491.6803457675. The cubic root of 991725931 is about 997.2343351494.

The spelling of 991725931 in words is "nine hundred ninety-one million, seven hundred twenty-five thousand, nine hundred thirty-one".