21974915 has 4 divisors (see below), whose sum is σ = 26369904. Its totient is φ = 17579928.

The previous prime is 21974899. The next prime is 21974917. The reversal of 21974915 is 51947912.

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

It is a cyclic number.

It is not a de Polignac number, because 21974915 - 2⁴ = 21974899 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21974917) 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, 2197487 + ... + 2197496.

It is an arithmetic number, because the mean of its divisors is an integer number (6592476).

Almost surely, 2^21974915 is an apocalyptic number.

21974915 is a deficient number, since it is larger than the sum of its proper divisors (4394989).

21974915 is an equidigital number, since it uses as much as digits as its factorization.

21974915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4394988.

The product of its digits is 22680, while the sum is 38.

The square root of 21974915 is about 4687.7409271418. The cubic root of 21974915 is about 280.0973938402.

The spelling of 21974915 in words is "twenty-one million, nine hundred seventy-four thousand, nine hundred fifteen".