21159971 has 4 divisors (see below), whose sum is σ = 24182832. Its totient is φ = 18137112.

The previous prime is 21159953. The next prime is 21159973. The reversal of 21159971 is 17995112.

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

It is not a de Polignac number, because 21159971 - 2⁶ = 21159907 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21159973) 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, 1511420 + ... + 1511433.

It is an arithmetic number, because the mean of its divisors is an integer number (6045708).

Almost surely, 2^21159971 is an apocalyptic number.

21159971 is a deficient number, since it is larger than the sum of its proper divisors (3022861).

21159971 is an equidigital number, since it uses as much as digits as its factorization.

21159971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3022860.

The product of its digits is 5670, while the sum is 35.

The square root of 21159971 is about 4599.9968478250. The cubic root of 21159971 is about 276.5911984285.

The spelling of 21159971 in words is "twenty-one million, one hundred fifty-nine thousand, nine hundred seventy-one".