21521423 has 12 divisors (see below), whose sum is σ = 27036240. Its totient is φ = 16769280.

The previous prime is 21521419. The next prime is 21521431. The reversal of 21521423 is 32412512.

It is not a de Polignac number, because 21521423 - 2² = 21521419 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21521395 and 21521404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521413) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11858 + ... + 13551.

It is an arithmetic number, because the mean of its divisors is an integer number (2253020).

Almost surely, 2^21521423 is an apocalyptic number.

21521423 is a deficient number, since it is larger than the sum of its proper divisors (5514817).

21521423 is a wasteful number, since it uses less digits than its factorization.

21521423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25438 (or 25427 counting only the distinct ones).

The product of its digits is 480, while the sum is 20.

The square root of 21521423 is about 4639.1187740777. The cubic root of 21521423 is about 278.1572140105.

Adding to 21521423 its reverse (32412512), we get a palindrome (53933935).

The spelling of 21521423 in words is "twenty-one million, five hundred twenty-one thousand, four hundred twenty-three".