21572216 has 8 divisors (see below), whose sum is σ = 40447920. Its totient is φ = 10786104.

The previous prime is 21572209. The next prime is 21572227. The reversal of 21572216 is 61227512.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 1348256 + ... + 1348271.

It is an arithmetic number, because the mean of its divisors is an integer number (5055990).

Almost surely, 2^21572216 is an apocalyptic number.

It is an amenable number.

21572216 is a deficient number, since it is larger than the sum of its proper divisors (18875704).

21572216 is a wasteful number, since it uses less digits than its factorization.

21572216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2696533 (or 2696529 counting only the distinct ones).

The product of its digits is 1680, while the sum is 26.

The square root of 21572216 is about 4644.5899711385. The cubic root of 21572216 is about 278.3758696111.

Adding to 21572216 its reverse (61227512), we get a palindrome (82799728).

The spelling of 21572216 in words is "twenty-one million, five hundred seventy-two thousand, two hundred sixteen".