31509981 has 12 divisors (see below), whose sum is σ = 46983040. Its totient is φ = 20328840.

The previous prime is 31509971. The next prime is 31509991. The reversal of 31509981 is 18990513.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (31509971) and next prime (31509991).

It is not a de Polignac number, because 31509981 - 2⁵ = 31509949 is a prime.

It is a super-2 number, since 2×31509981² = 1985757805240722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31509941) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 56191 + ... + 56748.

Almost surely, 2^31509981 is an apocalyptic number.

31509981 is a gapful number since it is divisible by the number (31) formed by its first and last digit.

It is an amenable number.

31509981 is a deficient number, since it is larger than the sum of its proper divisors (15473059).

31509981 is a wasteful number, since it uses less digits than its factorization.

31509981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112976 (or 112973 counting only the distinct ones).

The product of its (nonzero) digits is 9720, while the sum is 36.

The square root of 31509981 is about 5613.3751878883. The cubic root of 31509981 is about 315.8513327546.

It can be divided in two parts, 3150 and 9981, that added together give a palindrome (13131).

The spelling of 31509981 in words is "thirty-one million, five hundred nine thousand, nine hundred eighty-one".