21940823 has 2 divisors, whose sum is σ = 21940824. Its totient is φ = 21940822.

The previous prime is 21940817. The next prime is 21940837. The reversal of 21940823 is 32804912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21940823 - 2⁶ = 21940759 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21940813) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10970411 + 10970412.

It is an arithmetic number, because the mean of its divisors is an integer number (10970412).

Almost surely, 2^21940823 is an apocalyptic number.

21940823 is a deficient number, since it is larger than the sum of its proper divisors (1).

21940823 is an equidigital number, since it uses as much as digits as its factorization.

21940823 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 21940823 is about 4684.1032226030. The cubic root of 21940823 is about 279.9524706740.

The spelling of 21940823 in words is "twenty-one million, nine hundred forty thousand, eight hundred twenty-three".