21572215 has 16 divisors (see below), whose sum is σ = 29675520. Its totient is φ = 14747040.

The previous prime is 21572209. The next prime is 21572227. The reversal of 21572215 is 51227512.

It is not a de Polignac number, because 21572215 - 2¹⁹ = 21047927 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21572215.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13930 + ... + 15400.

It is an arithmetic number, because the mean of its divisors is an integer number (1854720).

Almost surely, 2^21572215 is an apocalyptic number.

21572215 is a deficient number, since it is larger than the sum of its proper divisors (8103305).

21572215 is a wasteful number, since it uses less digits than its factorization.

21572215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1902.

The product of its digits is 1400, while the sum is 25.

The square root of 21572215 is about 4644.5898634863. The cubic root of 21572215 is about 278.3758653097.

Adding to 21572215 its reverse (51227512), we get a palindrome (72799727).

The spelling of 21572215 in words is "twenty-one million, five hundred seventy-two thousand, two hundred fifteen".