31204021 has 2 divisors, whose sum is σ = 31204022. Its totient is φ = 31204020.

The previous prime is 31204013. The next prime is 31204037. The reversal of 31204021 is 12040213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 31203396 + 625 = 5586^2 + 25^2 .

It is an emirp because it is prime and its reverse (12040213) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31204021 - 2³ = 31204013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31203992 and 31204010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31204091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15602010 + 15602011.

It is an arithmetic number, because the mean of its divisors is an integer number (15602011).

Almost surely, 2^31204021 is an apocalyptic number.

It is an amenable number.

31204021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31204021 is an equidigital number, since it uses as much as digits as its factorization.

31204021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 31204021 is about 5586.0559431499. The cubic root of 31204021 is about 314.8257068884.

Adding to 31204021 its reverse (12040213), we get a palindrome (43244234).

The spelling of 31204021 in words is "thirty-one million, two hundred four thousand, twenty-one".