21472991 has 4 divisors (see below), whose sum is σ = 21837000. Its totient is φ = 21108984.

The previous prime is 21472973. The next prime is 21472993. The reversal of 21472991 is 19927412.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21472991 is a prime.

It is a super-2 number, since 2×21472991² = 922178684972162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21472993) 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, 181916 + ... + 182033.

It is an arithmetic number, because the mean of its divisors is an integer number (5459250).

Almost surely, 2^21472991 is an apocalyptic number.

21472991 is a deficient number, since it is larger than the sum of its proper divisors (364009).

21472991 is an equidigital number, since it uses as much as digits as its factorization.

21472991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 364008.

The product of its digits is 9072, while the sum is 35.

The square root of 21472991 is about 4633.8958771211. The cubic root of 21472991 is about 277.9484014789.

The spelling of 21472991 in words is "twenty-one million, four hundred seventy-two thousand, nine hundred ninety-one".