21213923 has 2 divisors, whose sum is σ = 21213924. Its totient is φ = 21213922.

The previous prime is 21213919. The next prime is 21213931. The reversal of 21213923 is 32931212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21213923 - 2² = 21213919 is a prime.

It is not a weakly prime, because it can be changed into another prime (21213623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606961 + 10606962.

It is an arithmetic number, because the mean of its divisors is an integer number (10606962).

Almost surely, 2^21213923 is an apocalyptic number.

21213923 is a deficient number, since it is larger than the sum of its proper divisors (1).

21213923 is an equidigital number, since it uses as much as digits as its factorization.

21213923 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 648, while the sum is 23.

The square root of 21213923 is about 4605.8574663140. The cubic root of 21213923 is about 276.8260756158.

The spelling of 21213923 in words is "twenty-one million, two hundred thirteen thousand, nine hundred twenty-three".