31198721 has 2 divisors, whose sum is σ = 31198722. Its totient is φ = 31198720.

The previous prime is 31198709. The next prime is 31198729. The reversal of 31198721 is 12789113.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27415696 + 3783025 = 5236^2 + 1945^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31198721 is a prime.

It is not a weakly prime, because it can be changed into another prime (31198729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15599360 + 15599361.

It is an arithmetic number, because the mean of its divisors is an integer number (15599361).

Almost surely, 2^31198721 is an apocalyptic number.

It is an amenable number.

31198721 is a deficient number, since it is larger than the sum of its proper divisors (1).

31198721 is an equidigital number, since it uses as much as digits as its factorization.

31198721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3024, while the sum is 32.

The square root of 31198721 is about 5585.5815274687. The cubic root of 31198721 is about 314.8078815070.

The spelling of 31198721 in words is "thirty-one million, one hundred ninety-eight thousand, seven hundred twenty-one".