31604561 has 2 divisors, whose sum is σ = 31604562. Its totient is φ = 31604560.

The previous prime is 31604557. The next prime is 31604603. The reversal of 31604561 is 16540613.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 28944400 + 2660161 = 5380^2 + 1631^2 .

It is an emirp because it is prime and its reverse (16540613) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31604561 - 2² = 31604557 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 31604561.

It is not a weakly prime, because it can be changed into another prime (31604501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15802280 + 15802281.

It is an arithmetic number, because the mean of its divisors is an integer number (15802281).

Almost surely, 2^31604561 is an apocalyptic number.

It is an amenable number.

31604561 is a deficient number, since it is larger than the sum of its proper divisors (1).

31604561 is an equidigital number, since it uses as much as digits as its factorization.

31604561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 31604561 is about 5621.7933971287. The cubic root of 31604561 is about 316.1670356823.

The spelling of 31604561 in words is "thirty-one million, six hundred four thousand, five hundred sixty-one".