31978381 has 2 divisors, whose sum is σ = 31978382. Its totient is φ = 31978380.

The previous prime is 31978367. The next prime is 31978399. The reversal of 31978381 is 18387913.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 23328900 + 8649481 = 4830^2 + 2941^2 .

It is a cyclic number.

It is not a de Polignac number, because 31978381 - 2¹¹ = 31976333 is a prime.

It is a super-2 number, since 2×31978381² = 2045233702762322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31978321) 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 as a sum of consecutive naturals, namely, 15989190 + 15989191.

It is an arithmetic number, because the mean of its divisors is an integer number (15989191).

Almost surely, 2^31978381 is an apocalyptic number.

31978381 is the 3577-th centered pentagonal number.

It is an amenable number.

31978381 is a deficient number, since it is larger than the sum of its proper divisors (1).

31978381 is an equidigital number, since it uses as much as digits as its factorization.

31978381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 40.

The square root of 31978381 is about 5654.9430589529. The cubic root of 31978381 is about 317.4086984049.

The spelling of 31978381 in words is "thirty-one million, nine hundred seventy-eight thousand, three hundred eighty-one".