21523623 has 16 divisors (see below), whose sum is σ = 31449600. Its totient is φ = 12985280.

The previous prime is 21523609. The next prime is 21523631. The reversal of 21523623 is 32632512.

It is not a de Polignac number, because 21523623 - 2⁵ = 21523591 is a prime.

It is a super-2 number, since 2×21523623² = 926532694092258, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21523593 and 21523602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21524623) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6523 + ... + 9251.

It is an arithmetic number, because the mean of its divisors is an integer number (1965600).

Almost surely, 2^21523623 is an apocalyptic number.

21523623 is a deficient number, since it is larger than the sum of its proper divisors (9925977).

21523623 is a wasteful number, since it uses less digits than its factorization.

21523623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2982.

The product of its digits is 2160, while the sum is 24.

The square root of 21523623 is about 4639.3558820164. The cubic root of 21523623 is about 278.1666917763.

Subtracting 21523623 from its reverse (32632512), we obtain a square (11108889 = 3333²).

It can be divided in two parts, 2152 and 3623, that added together give a palindrome (5775).

The spelling of 21523623 in words is "twenty-one million, five hundred twenty-three thousand, six hundred twenty-three".