31403921 has 2 divisors, whose sum is σ = 31403922. Its totient is φ = 31403920.

The previous prime is 31403893. The next prime is 31403969. The reversal of 31403921 is 12930413.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27040000 + 4363921 = 5200^2 + 2089^2 .

It is an emirp because it is prime and its reverse (12930413) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31403921 - 2⁶ = 31403857 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (31403321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15701960 + 15701961.

It is an arithmetic number, because the mean of its divisors is an integer number (15701961).

Almost surely, 2^31403921 is an apocalyptic number.

It is an amenable number.

31403921 is a deficient number, since it is larger than the sum of its proper divisors (1).

31403921 is an equidigital number, since it uses as much as digits as its factorization.

31403921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648, while the sum is 23.

The square root of 31403921 is about 5603.9201457551. The cubic root of 31403921 is about 315.4965578875.

The spelling of 31403921 in words is "thirty-one million, four hundred three thousand, nine hundred twenty-one".