21815016 has 16 divisors (see below), whose sum is σ = 54537600. Its totient is φ = 7271664.

The previous prime is 21815011. The next prime is 21815023. The reversal of 21815016 is 61051812.

It is a Harshad number since it is a multiple of its sum of digits (24), and also a Moran number because the ratio is a prime number: 908959 = 21815016 / (2 + 1 + 8 + 1 + 5 + 0 + 1 + 6).

It is not an unprimeable number, because it can be changed into a prime (21815011) 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, 454456 + ... + 454503.

It is an arithmetic number, because the mean of its divisors is an integer number (3408600).

Almost surely, 2^21815016 is an apocalyptic number.

It is an amenable number.

21815016 is an abundant number, since it is smaller than the sum of its proper divisors (32722584).

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

21815016 is a wasteful number, since it uses less digits than its factorization.

21815016 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 908968 (or 908964 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 24.

The square root of 21815016 is about 4670.6547720850. The cubic root of 21815016 is about 279.4163693624.

Adding to 21815016 its reverse (61051812), we get a palindrome (82866828).

The spelling of 21815016 in words is "twenty-one million, eight hundred fifteen thousand, sixteen".