21642971 has 4 divisors (see below), whose sum is σ = 24734832. Its totient is φ = 18551112.

The previous prime is 21642953. The next prime is 21642979. The reversal of 21642971 is 17924612.

It is a happy number.

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 21642971 - 2¹⁰ = 21641947 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21642979) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1545920 + ... + 1545933.

It is an arithmetic number, because the mean of its divisors is an integer number (6183708).

Almost surely, 2^21642971 is an apocalyptic number.

21642971 is a deficient number, since it is larger than the sum of its proper divisors (3091861).

21642971 is an equidigital number, since it uses as much as digits as its factorization.

21642971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3091860.

The product of its digits is 6048, while the sum is 32.

The square root of 21642971 is about 4652.2006620523. The cubic root of 21642971 is about 278.6798870496.

The spelling of 21642971 in words is "twenty-one million, six hundred forty-two thousand, nine hundred seventy-one".