31389931 has 4 divisors (see below), whose sum is σ = 31667832. Its totient is φ = 31112032.

The previous prime is 31389923. The next prime is 31389961. The reversal of 31389931 is 13998313.

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 31389931 - 2³ = 31389923 is a prime.

It is a super-2 number, since 2×31389931² = 1970655536369522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31389901) 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, 138781 + ... + 139006.

It is an arithmetic number, because the mean of its divisors is an integer number (7916958).

Almost surely, 2^31389931 is an apocalyptic number.

31389931 is a deficient number, since it is larger than the sum of its proper divisors (277901).

31389931 is a wasteful number, since it uses less digits than its factorization.

31389931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 277900.

The product of its digits is 17496, while the sum is 37.

The square root of 31389931 is about 5602.6717733596. The cubic root of 31389931 is about 315.4497011862.

The spelling of 31389931 in words is "thirty-one million, three hundred eighty-nine thousand, nine hundred thirty-one".