31828721 has 2 divisors, whose sum is σ = 31828722. Its totient is φ = 31828720.

The previous prime is 31828691. The next prime is 31828733. The reversal of 31828721 is 12782813.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21492496 + 10336225 = 4636^2 + 3215^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31828721 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (31828421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15914360 + 15914361.

It is an arithmetic number, because the mean of its divisors is an integer number (15914361).

Almost surely, 2^31828721 is an apocalyptic number.

It is an amenable number.

31828721 is a deficient number, since it is larger than the sum of its proper divisors (1).

31828721 is an equidigital number, since it uses as much as digits as its factorization.

31828721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5376, while the sum is 32.

The square root of 31828721 is about 5641.6948694519. The cubic root of 31828721 is about 316.9127624688.

The spelling of 31828721 in words is "thirty-one million, eight hundred twenty-eight thousand, seven hundred twenty-one".