21929393 has 2 divisors, whose sum is σ = 21929394. Its totient is φ = 21929392.

The previous prime is 21929389. The next prime is 21929437. The reversal of 21929393 is 39392912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18421264 + 3508129 = 4292^2 + 1873^2 .

It is a cyclic number.

It is not a de Polignac number, because 21929393 - 2² = 21929389 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21929293) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10964696 + 10964697.

It is an arithmetic number, because the mean of its divisors is an integer number (10964697).

Almost surely, 2^21929393 is an apocalyptic number.

It is an amenable number.

21929393 is a deficient number, since it is larger than the sum of its proper divisors (1).

21929393 is an equidigital number, since it uses as much as digits as its factorization.

21929393 is an evil number, because the sum of its binary digits is even.

The product of its digits is 26244, while the sum is 38.

The square root of 21929393 is about 4682.8829795330. The cubic root of 21929393 is about 279.9038487884.

It can be divided in two parts, 21929 and 393, that added together give a palindrome (22322).

The spelling of 21929393 in words is "twenty-one million, nine hundred twenty-nine thousand, three hundred ninety-three".