21370031 has 2 divisors, whose sum is σ = 21370032. Its totient is φ = 21370030.

The previous prime is 21370021. The next prime is 21370033. The reversal of 21370031 is 13007312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21370031 is a prime.

It is a super-2 number, since 2×21370031² = 913356449881922, which contains 22 as substring.

Together with 21370033, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21369991 and 21370009.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21370033) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10685015 + 10685016.

It is an arithmetic number, because the mean of its divisors is an integer number (10685016).

Almost surely, 2^21370031 is an apocalyptic number.

21370031 is a deficient number, since it is larger than the sum of its proper divisors (1).

21370031 is an equidigital number, since it uses as much as digits as its factorization.

21370031 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 126, while the sum is 17.

The square root of 21370031 is about 4622.7730854975. The cubic root of 21370031 is about 277.5034482703.

Adding to 21370031 its reverse (13007312), we get a palindrome (34377343).

The spelling of 21370031 in words is "twenty-one million, three hundred seventy thousand, thirty-one".