31630021 has 2 divisors, whose sum is σ = 31630022. Its totient is φ = 31630020.

The previous prime is 31630019. The next prime is 31630031. The reversal of 31630021 is 12003613.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16892100 + 14737921 = 4110^2 + 3839^2 .

It is an emirp because it is prime and its reverse (12003613) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31630021 - 2¹ = 31630019 is a prime.

Together with 31630019, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 31629977 and 31630004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31630031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15815010 + 15815011.

It is an arithmetic number, because the mean of its divisors is an integer number (15815011).

Almost surely, 2^31630021 is an apocalyptic number.

It is an amenable number.

31630021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31630021 is an equidigital number, since it uses as much as digits as its factorization.

31630021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 108, while the sum is 16.

The square root of 31630021 is about 5624.0573432354. The cubic root of 31630021 is about 316.2519121675.

Adding to 31630021 its reverse (12003613), we get a palindrome (43633634).

The spelling of 31630021 in words is "thirty-one million, six hundred thirty thousand, twenty-one".