21615201 has 16 divisors (see below), whose sum is σ = 32206720. Its totient is φ = 14327280.

The previous prime is 21615173. The next prime is 21615203. The reversal of 21615201 is 10251612.

It is not a de Polignac number, because 21615201 - 2⁷ = 21615073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21615203) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2676 + ... + 7098.

It is an arithmetic number, because the mean of its divisors is an integer number (2012920).

Almost surely, 2^21615201 is an apocalyptic number.

It is an amenable number.

21615201 is a deficient number, since it is larger than the sum of its proper divisors (10591519).

21615201 is a wasteful number, since it uses less digits than its factorization.

21615201 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4613 (or 4607 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21615201 is about 4649.2150950456. The cubic root of 21615201 is about 278.5606450602.

Adding to 21615201 its reverse (10251612), we get a palindrome (31866813).

The spelling of 21615201 in words is "twenty-one million, six hundred fifteen thousand, two hundred one".