21502231 has 2 divisors, whose sum is σ = 21502232. Its totient is φ = 21502230.

The previous prime is 21502219. The next prime is 21502241. The reversal of 21502231 is 13220512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21502231 - 2⁵ = 21502199 is a prime.

It is a super-2 number, since 2×21502231² = 924691875954722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21502241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10751115 + 10751116.

It is an arithmetic number, because the mean of its divisors is an integer number (10751116).

Almost surely, 2^21502231 is an apocalyptic number.

21502231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21502231 is an equidigital number, since it uses as much as digits as its factorization.

21502231 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21502231 is about 4637.0498164242. The cubic root of 21502231 is about 278.0745060208.

Adding to 21502231 its reverse (13220512), we get a palindrome (34722743).

The spelling of 21502231 in words is "twenty-one million, five hundred two thousand, two hundred thirty-one".