21572366 has 4 divisors (see below), whose sum is σ = 32358552. Its totient is φ = 10786182.

The previous prime is 21572363. The next prime is 21572387. The reversal of 21572366 is 66327512.

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21572363) 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, 5393090 + ... + 5393093.

It is an arithmetic number, because the mean of its divisors is an integer number (8089638).

Almost surely, 2^21572366 is an apocalyptic number.

21572366 is a deficient number, since it is larger than the sum of its proper divisors (10786186).

21572366 is a wasteful number, since it uses less digits than its factorization.

21572366 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10786185.

The product of its digits is 15120, while the sum is 32.

The square root of 21572366 is about 4644.6061189298. The cubic root of 21572366 is about 278.3765148281.

Adding to 21572366 its reverse (66327512), we get a palindrome (87899878).

The spelling of 21572366 in words is "twenty-one million, five hundred seventy-two thousand, three hundred sixty-six".