21329923 has 2 divisors, whose sum is σ = 21329924. Its totient is φ = 21329922.

The previous prime is 21329911. The next prime is 21329927. The reversal of 21329923 is 32992312.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21329923 is a prime.

It is not a weakly prime, because it can be changed into another prime (21329927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10664961 + 10664962.

It is an arithmetic number, because the mean of its divisors is an integer number (10664962).

Almost surely, 2^21329923 is an apocalyptic number.

21329923 is a deficient number, since it is larger than the sum of its proper divisors (1).

21329923 is an equidigital number, since it uses as much as digits as its factorization.

21329923 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5832, while the sum is 31.

The square root of 21329923 is about 4618.4329593489. The cubic root of 21329923 is about 277.3297302460.

The spelling of 21329923 in words is "twenty-one million, three hundred twenty-nine thousand, nine hundred twenty-three".