21331316 has 12 divisors (see below), whose sum is σ = 38240580. Its totient is φ = 10405440.

The previous prime is 21331313. The next prime is 21331333. The reversal of 21331316 is 61313312.

21331316 = T₁₈₄ + T₁₈₅ + ... + T₅₁₁.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 7862416 + 13468900 = 2804^2 + 3670^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21331313) 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, 64871 + ... + 65198.

It is an arithmetic number, because the mean of its divisors is an integer number (3186715).

Almost surely, 2^21331316 is an apocalyptic number.

It is an amenable number.

21331316 is a deficient number, since it is larger than the sum of its proper divisors (16909264).

21331316 is a wasteful number, since it uses less digits than its factorization.

21331316 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130114 (or 130112 counting only the distinct ones).

The product of its digits is 324, while the sum is 20.

The square root of 21331316 is about 4618.5837656147. The cubic root of 21331316 is about 277.3357673346.

Adding to 21331316 its reverse (61313312), we get a palindrome (82644628).

The spelling of 21331316 in words is "twenty-one million, three hundred thirty-one thousand, three hundred sixteen".