21523210 has 8 divisors (see below), whose sum is σ = 38741796. Its totient is φ = 8609280.

The previous prime is 21523171. The next prime is 21523261. The reversal of 21523210 is 1232512.

It can be written as a sum of positive squares in 2 ways, for example, as 20133169 + 1390041 = 4487^2 + 1179^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1076151 + ... + 1076170.

Almost surely, 2^21523210 is an apocalyptic number.

21523210 is a deficient number, since it is larger than the sum of its proper divisors (17218586).

21523210 is a wasteful number, since it uses less digits than its factorization.

21523210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2152328.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21523210 is about 4639.3113713136. The cubic root of 21523210 is about 278.1649125904.

Adding to 21523210 its reverse (1232512), we get a palindrome (22755722).

The spelling of 21523210 in words is "twenty-one million, five hundred twenty-three thousand, two hundred ten".