21423253 has 4 divisors (see below), whose sum is σ = 21554848. Its totient is φ = 21291660.

The previous prime is 21423251. The next prime is 21423271. The reversal of 21423253 is 35232412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21423253 - 2¹ = 21423251 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21423251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65553 + ... + 65878.

It is an arithmetic number, because the mean of its divisors is an integer number (5388712).

Almost surely, 2^21423253 is an apocalyptic number.

It is an amenable number.

21423253 is a deficient number, since it is larger than the sum of its proper divisors (131595).

21423253 is a wasteful number, since it uses less digits than its factorization.

21423253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131594.

The product of its digits is 1440, while the sum is 22.

The square root of 21423253 is about 4628.5260072727. The cubic root of 21423253 is about 277.7336311294.

Adding to 21423253 its reverse (35232412), we get a palindrome (56655665).

The spelling of 21423253 in words is "twenty-one million, four hundred twenty-three thousand, two hundred fifty-three".