21975217 has 4 divisors (see below), whose sum is σ = 23972976. Its totient is φ = 19977460.

The previous prime is 21975167. The next prime is 21975287. The reversal of 21975217 is 71257912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21975217 - 2¹¹ = 21973169 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21975287) 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, 998863 + ... + 998884.

It is an arithmetic number, because the mean of its divisors is an integer number (5993244).

Almost surely, 2^21975217 is an apocalyptic number.

It is an amenable number.

21975217 is a deficient number, since it is larger than the sum of its proper divisors (1997759).

21975217 is a wasteful number, since it uses less digits than its factorization.

21975217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1997758.

The product of its digits is 8820, while the sum is 34.

The square root of 21975217 is about 4687.7731387088. The cubic root of 21975217 is about 280.0986769551.

The spelling of 21975217 in words is "twenty-one million, nine hundred seventy-five thousand, two hundred seventeen".