21959947 has 4 divisors (see below), whose sum is σ = 21990640. Its totient is φ = 21929256.

The previous prime is 21959941. The next prime is 21959957. The reversal of 21959947 is 74995912.

It is a happy number.

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-21959947 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21959897 and 21959906.

It is not an unprimeable number, because it can be changed into a prime (21959941) 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, 14247 + ... + 15712.

It is an arithmetic number, because the mean of its divisors is an integer number (5497660).

Almost surely, 2^21959947 is an apocalyptic number.

21959947 is a deficient number, since it is larger than the sum of its proper divisors (30693).

21959947 is an equidigital number, since it uses as much as digits as its factorization.

21959947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30692.

The product of its digits is 204120, while the sum is 46.

The square root of 21959947 is about 4686.1441505784. The cubic root of 21959947 is about 280.0337841888.

The spelling of 21959947 in words is "twenty-one million, nine hundred fifty-nine thousand, nine hundred forty-seven".