31090021 has 2 divisors, whose sum is σ = 31090022. Its totient is φ = 31090020.

The previous prime is 31089941. The next prime is 31090063. The reversal of 31090021 is 12009013.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 30305025 + 784996 = 5505^2 + 886^2 .

It is a cyclic number.

It is not a de Polignac number, because 31090021 - 2¹³ = 31081829 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31089977 and 31090004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31090091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15545010 + 15545011.

It is an arithmetic number, because the mean of its divisors is an integer number (15545011).

Almost surely, 2^31090021 is an apocalyptic number.

It is an amenable number.

31090021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31090021 is an equidigital number, since it uses as much as digits as its factorization.

31090021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 54, while the sum is 16.

The square root of 31090021 is about 5575.8426269040. The cubic root of 31090021 is about 314.4418468914.

Adding to 31090021 its reverse (12009013), we get a palindrome (43099034).

The spelling of 31090021 in words is "thirty-one million, ninety thousand, twenty-one".