21804947 has 4 divisors (see below), whose sum is σ = 21918120. Its totient is φ = 21691776.

The previous prime is 21804941. The next prime is 21804953. The reversal of 21804947 is 74940812.

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

It is an interprime number because it is at equal distance from previous prime (21804941) and next prime (21804953).

It is a cyclic number.

It is not a de Polignac number, because 21804947 - 2¹⁴ = 21788563 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21804941) 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, 56297 + ... + 56682.

It is an arithmetic number, because the mean of its divisors is an integer number (5479530).

Almost surely, 2^21804947 is an apocalyptic number.

21804947 is a deficient number, since it is larger than the sum of its proper divisors (113173).

21804947 is a wasteful number, since it uses less digits than its factorization.

21804947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113172.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 21804947 is about 4669.5767474151. The cubic root of 21804947 is about 279.3733733454.

The spelling of 21804947 in words is "twenty-one million, eight hundred four thousand, nine hundred forty-seven".