21215315 has 32 divisors (see below), whose sum is σ = 29970432. Its totient is φ = 14256000.

The previous prime is 21215309. The next prime is 21215321. The reversal of 21215315 is 51351212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21215309) and next prime (21215321).

It is a de Polignac number, because none of the positive numbers 2^k-21215315 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 38945 + ... + 39485.

It is an arithmetic number, because the mean of its divisors is an integer number (936576).

Almost surely, 2^21215315 is an apocalyptic number.

21215315 is a deficient number, since it is larger than the sum of its proper divisors (8755117).

21215315 is a wasteful number, since it uses less digits than its factorization.

21215315 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 611.

The product of its digits is 300, while the sum is 20.

The square root of 21215315 is about 4606.0085757628. The cubic root of 21215315 is about 276.8321303417.

Adding to 21215315 its reverse (51351212), we get a palindrome (72566527).

The spelling of 21215315 in words is "twenty-one million, two hundred fifteen thousand, three hundred fifteen".