31421981 has 2 divisors, whose sum is σ = 31421982. Its totient is φ = 31421980.

The previous prime is 31421977. The next prime is 31421987. The reversal of 31421981 is 18912413.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18705625 + 12716356 = 4325^2 + 3566^2 .

It is a cyclic number.

It is not a de Polignac number, because 31421981 - 2² = 31421977 is a prime.

It is a super-2 number, since 2×31421981² = 1974681779928722, 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 (31421987) 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, 15710990 + 15710991.

It is an arithmetic number, because the mean of its divisors is an integer number (15710991).

Almost surely, 2^31421981 is an apocalyptic number.

It is an amenable number.

31421981 is a deficient number, since it is larger than the sum of its proper divisors (1).

31421981 is an equidigital number, since it uses as much as digits as its factorization.

31421981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 29.

The square root of 31421981 is about 5605.5312861494. The cubic root of 31421981 is about 315.5570256650.

The spelling of 31421981 in words is "thirty-one million, four hundred twenty-one thousand, nine hundred eighty-one".