21917023 has 2 divisors, whose sum is σ = 21917024. Its totient is φ = 21917022.

The previous prime is 21917003. The next prime is 21917113. The reversal of 21917023 is 32071912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21917023 - 2⁵ = 21916991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21917003) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10958511 + 10958512.

It is an arithmetic number, because the mean of its divisors is an integer number (10958512).

Almost surely, 2^21917023 is an apocalyptic number.

21917023 is a deficient number, since it is larger than the sum of its proper divisors (1).

21917023 is an equidigital number, since it uses as much as digits as its factorization.

21917023 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 21917023 is about 4681.5620256491. The cubic root of 21917023 is about 279.8512092125.

Adding to 21917023 its reverse (32071912), we get a palindrome (53988935).

The spelling of 21917023 in words is "twenty-one million, nine hundred seventeen thousand, twenty-three".