21523130 has 16 divisors (see below), whose sum is σ = 38991240. Its totient is φ = 8553792.

The previous prime is 21523093. The next prime is 21523171. The reversal of 21523130 is 3132512.

It can be written as a sum of positive squares in 4 ways, for example, as 18757561 + 2765569 = 4331^2 + 1663^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21523099 and 21523108.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5285 + ... + 8424.

Almost surely, 2^21523130 is an apocalyptic number.

21523130 is a deficient number, since it is larger than the sum of its proper divisors (17468110).

21523130 is a wasteful number, since it uses less digits than its factorization.

21523130 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13873.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 21523130 is about 4639.3027493364. The cubic root of 21523130 is about 278.1645679513.

Adding to 21523130 its reverse (3132512), we get a palindrome (24655642).

The spelling of 21523130 in words is "twenty-one million, five hundred twenty-three thousand, one hundred thirty".