21893813 has 2 divisors, whose sum is σ = 21893814. Its totient is φ = 21893812.

The previous prime is 21893777. The next prime is 21893827. The reversal of 21893813 is 31839812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20857489 + 1036324 = 4567^2 + 1018^2 .

It is a cyclic number.

It is not a de Polignac number, because 21893813 - 2⁶ = 21893749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21893513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10946906 + 10946907.

It is an arithmetic number, because the mean of its divisors is an integer number (10946907).

Almost surely, 2^21893813 is an apocalyptic number.

It is an amenable number.

21893813 is a deficient number, since it is larger than the sum of its proper divisors (1).

21893813 is an equidigital number, since it uses as much as digits as its factorization.

21893813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 35.

The square root of 21893813 is about 4679.0824955326. The cubic root of 21893813 is about 279.7523873856.

The spelling of 21893813 in words is "twenty-one million, eight hundred ninety-three thousand, eight hundred thirteen".