21917963 has 4 divisors (see below), whose sum is σ = 23071560. Its totient is φ = 20764368.

The previous prime is 21917927. The next prime is 21917977. The reversal of 21917963 is 36971912.

It is a happy number.

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 21917963 - 2²⁴ = 5140747 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21917923) 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, 576770 + ... + 576807.

It is an arithmetic number, because the mean of its divisors is an integer number (5767890).

Almost surely, 2^21917963 is an apocalyptic number.

21917963 is a deficient number, since it is larger than the sum of its proper divisors (1153597).

21917963 is a wasteful number, since it uses less digits than its factorization.

21917963 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1153596.

The product of its digits is 20412, while the sum is 38.

The square root of 21917963 is about 4681.6624184151. The cubic root of 21917963 is about 279.8552100049.

The spelling of 21917963 in words is "twenty-one million, nine hundred seventeen thousand, nine hundred sixty-three".