21397253 has 2 divisors, whose sum is σ = 21397254. Its totient is φ = 21397252.

The previous prime is 21397217. The next prime is 21397279. The reversal of 21397253 is 35279312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12623809 + 8773444 = 3553^2 + 2962^2 .

It is a cyclic number.

It is not a de Polignac number, because 21397253 - 2¹⁸ = 21135109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21397283) 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, 10698626 + 10698627.

It is an arithmetic number, because the mean of its divisors is an integer number (10698627).

Almost surely, 2^21397253 is an apocalyptic number.

It is an amenable number.

21397253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21397253 is an equidigital number, since it uses as much as digits as its factorization.

21397253 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11340, while the sum is 32.

The square root of 21397253 is about 4625.7164850432. The cubic root of 21397253 is about 277.6212299357.

The spelling of 21397253 in words is "twenty-one million, three hundred ninety-seven thousand, two hundred fifty-three".