21551364 has 18 divisors (see below), whose sum is σ = 54477150. Its totient is φ = 7183776.

The previous prime is 21551357. The next prime is 21551401. The reversal of 21551364 is 46315512.

It can be written as a sum of positive squares in only one way, i.e., 20629764 + 921600 = 4542^2 + 960^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×21551364² = 928922580520992, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 299289 + ... + 299360.

Almost surely, 2^21551364 is an apocalyptic number.

It is an amenable number.

21551364 is an abundant number, since it is smaller than the sum of its proper divisors (32925786).

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

21551364 is a wasteful number, since it uses less digits than its factorization.

21551364 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 598659 (or 598654 counting only the distinct ones).

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

The square root of 21551364 is about 4642.3446662220. The cubic root of 21551364 is about 278.2861467173.

Adding to 21551364 its reverse (46315512), we get a palindrome (67866876).

The spelling of 21551364 in words is "twenty-one million, five hundred fifty-one thousand, three hundred sixty-four".