31388981 has 8 divisors (see below), whose sum is σ = 33851160. Its totient is φ = 28933632.

The previous prime is 31388977. The next prime is 31388983. The reversal of 31388981 is 18988313.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1522756 + 29866225 = 1234^2 + 5465^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 31388981 - 2² = 31388977 is a prime.

It is a super-2 number, since 2×31388981² = 1970536256436722, 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 (31388983) 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 7 ways as a sum of consecutive naturals, for example, 11921 + ... + 14313.

It is an arithmetic number, because the mean of its divisors is an integer number (4231395).

Almost surely, 2^31388981 is an apocalyptic number.

It is an amenable number.

31388981 is a deficient number, since it is larger than the sum of its proper divisors (2462179).

31388981 is a wasteful number, since it uses less digits than its factorization.

31388981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3415.

The product of its digits is 41472, while the sum is 41.

The square root of 31388981 is about 5602.5869917387. The cubic root of 31388981 is about 315.4465188469.

It can be divided in two parts, 31388 and 981, that multiplied together give a triangular number (30791628 = T₇₈₄₇).

The spelling of 31388981 in words is "thirty-one million, three hundred eighty-eight thousand, nine hundred eighty-one".