21051616 has 12 divisors (see below), whose sum is σ = 41445432. Its totient is φ = 10525792.

The previous prime is 21051599. The next prime is 21051623. The reversal of 21051616 is 61615012.

It is a super-2 number, since 2×21051616² = 886341072422912, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 328900 + ... + 328963.

It is an arithmetic number, because the mean of its divisors is an integer number (3453786).

Almost surely, 2^21051616 is an apocalyptic number.

It is an amenable number.

21051616 is a deficient number, since it is larger than the sum of its proper divisors (20393816).

21051616 is an equidigital number, since it uses as much as digits as its factorization.

21051616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 657873 (or 657865 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 21051616 is about 4588.2040059265. The cubic root of 21051616 is about 276.1182717921.

Adding to 21051616 its reverse (61615012), we get a palindrome (82666628).

It can be divided in two parts, 2105 and 1616, that added together give a square (3721 = 61²).

The spelling of 21051616 in words is "twenty-one million, fifty-one thousand, six hundred sixteen".