21515364 has 72 divisors (see below), whose sum is σ = 60499712. Its totient is φ = 6402240.

The previous prime is 21515359. The next prime is 21515369. The reversal of 21515364 is 46351512.

It is an interprime number because it is at equal distance from previous prime (21515359) and next prime (21515369).

It is not an unprimeable number, because it can be changed into a prime (21515369) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13767 + ... + 15249.

Almost surely, 2^21515364 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21515364, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30249856).

21515364 is an abundant number, since it is smaller than the sum of its proper divisors (38984348).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21515364 is a wasteful number, since it uses less digits than its factorization.

21515364 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1537 (or 1532 counting only the distinct ones).

The product of its digits is 3600, while the sum is 27.

The square root of 21515364 is about 4638.4656946020. The cubic root of 21515364 is about 278.1311080424.

Adding to 21515364 its reverse (46351512), we get a palindrome (67866876).

The spelling of 21515364 in words is "twenty-one million, five hundred fifteen thousand, three hundred sixty-four".