21947957 has 4 divisors (see below), whose sum is σ = 22902240. Its totient is φ = 20993676.

The previous prime is 21947951. The next prime is 21947963. The reversal of 21947957 is 75974912.

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 an interprime number because it is at equal distance from previous prime (21947951) and next prime (21947963).

It is a cyclic number.

It is not a de Polignac number, because 21947957 - 2²² = 17753653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21947951) 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, 477107 + ... + 477152.

It is an arithmetic number, because the mean of its divisors is an integer number (5725560).

Almost surely, 2^21947957 is an apocalyptic number.

It is an amenable number.

21947957 is a deficient number, since it is larger than the sum of its proper divisors (954283).

21947957 is an equidigital number, since it uses as much as digits as its factorization.

21947957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 954282.

The product of its digits is 158760, while the sum is 44.

The square root of 21947957 is about 4684.8646725386. The cubic root of 21947957 is about 279.9828093187.

The spelling of 21947957 in words is "twenty-one million, nine hundred forty-seven thousand, nine hundred fifty-seven".