21572371 has 4 divisors (see below), whose sum is σ = 22841352. Its totient is φ = 20303392.

The previous prime is 21572363. The next prime is 21572387. The reversal of 21572371 is 17327512.

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

It is a cyclic number.

It is not a de Polignac number, because 21572371 - 2³ = 21572363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21573371) 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 in 3 ways as a sum of consecutive naturals, for example, 634465 + ... + 634498.

It is an arithmetic number, because the mean of its divisors is an integer number (5710338).

Almost surely, 2^21572371 is an apocalyptic number.

21572371 is a deficient number, since it is larger than the sum of its proper divisors (1268981).

21572371 is a wasteful number, since it uses less digits than its factorization.

21572371 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1268980.

The product of its digits is 2940, while the sum is 28.

The square root of 21572371 is about 4644.6066571885. The cubic root of 21572371 is about 278.3765363353.

Adding to 21572371 its reverse (17327512), we get a palindrome (38899883).

The spelling of 21572371 in words is "twenty-one million, five hundred seventy-two thousand, three hundred seventy-one".