31831381 has 2 divisors, whose sum is σ = 31831382. Its totient is φ = 31831380.

The previous prime is 31831343. The next prime is 31831409. The reversal of 31831381 is 18313813.

It is an a-pointer prime, because the next prime (31831409) can be obtained adding 31831381 to its sum of digits (28).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27730756 + 4100625 = 5266^2 + 2025^2 .

It is a cyclic number.

It is not a de Polignac number, because 31831381 - 2¹¹ = 31829333 is a prime.

It is a super-2 number, since 2×31831381² = 2026473632734322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31831301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15915690 + 15915691.

It is an arithmetic number, because the mean of its divisors is an integer number (15915691).

Almost surely, 2^31831381 is an apocalyptic number.

It is an amenable number.

31831381 is a deficient number, since it is larger than the sum of its proper divisors (1).

31831381 is an equidigital number, since it uses as much as digits as its factorization.

31831381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 28.

The square root of 31831381 is about 5641.9306092862. The cubic root of 31831381 is about 316.9215906010.

The spelling of 31831381 in words is "thirty-one million, eight hundred thirty-one thousand, three hundred eighty-one".