21931223 has 2 divisors, whose sum is σ = 21931224. Its totient is φ = 21931222.

The previous prime is 21931219. The next prime is 21931237. The reversal of 21931223 is 32213912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21931223 - 2² = 21931219 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21931243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10965611 + 10965612.

It is an arithmetic number, because the mean of its divisors is an integer number (10965612).

Almost surely, 2^21931223 is an apocalyptic number.

21931223 is a deficient number, since it is larger than the sum of its proper divisors (1).

21931223 is an equidigital number, since it uses as much as digits as its factorization.

21931223 is an evil number, because the sum of its binary digits is even.

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

The square root of 21931223 is about 4683.0783679114. The cubic root of 21931223 is about 279.9116345306.

The spelling of 21931223 in words is "twenty-one million, nine hundred thirty-one thousand, two hundred twenty-three".