21572266 has 4 divisors (see below), whose sum is σ = 32358402. Its totient is φ = 10786132.

The previous prime is 21572261. The next prime is 21572267. The reversal of 21572266 is 66227512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 13535041 + 8037225 = 3679^2 + 2835^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21572261) 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 as a sum of consecutive naturals, namely, 5393065 + ... + 5393068.

Almost surely, 2^21572266 is an apocalyptic number.

21572266 is the 2938-th centered pentagonal number.

21572266 is a deficient number, since it is larger than the sum of its proper divisors (10786136).

21572266 is a wasteful number, since it uses less digits than its factorization.

21572266 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10786135.

The product of its digits is 10080, while the sum is 31.

The square root of 21572266 is about 4644.5953537418. The cubic root of 21572266 is about 278.3760846838.

Adding to 21572266 its reverse (66227512), we get a palindrome (87799778).

The spelling of 21572266 in words is "twenty-one million, five hundred seventy-two thousand, two hundred sixty-six".