21625231 has 2 divisors, whose sum is σ = 21625232. Its totient is φ = 21625230.

The previous prime is 21625229. The next prime is 21625237. The reversal of 21625231 is 13252612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21625231 - 2¹ = 21625229 is a prime.

It is a super-2 number, since 2×21625231² = 935301231606722, which contains 22 as substring.

Together with 21625229, it forms a pair of twin primes.

It is equal to p_1367014 and since 21625231 and 1367014 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21625237) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10812615 + 10812616.

It is an arithmetic number, because the mean of its divisors is an integer number (10812616).

Almost surely, 2^21625231 is an apocalyptic number.

21625231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21625231 is an equidigital number, since it uses as much as digits as its factorization.

21625231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 720, while the sum is 22.

The square root of 21625231 is about 4650.2936466421. The cubic root of 21625231 is about 278.6037247926.

Adding to 21625231 its reverse (13252612), we get a palindrome (34877843).

The spelling of 21625231 in words is "twenty-one million, six hundred twenty-five thousand, two hundred thirty-one".