21929993 has 2 divisors, whose sum is σ = 21929994. Its totient is φ = 21929992.

The previous prime is 21929987. The next prime is 21930101. The reversal of 21929993 is 39992912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12020089 + 9909904 = 3467^2 + 3148^2 .

It is a cyclic number.

It is not a de Polignac number, because 21929993 - 2⁴ = 21929977 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21929903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10964996 + 10964997.

It is an arithmetic number, because the mean of its divisors is an integer number (10964997).

Almost surely, 2^21929993 is an apocalyptic number.

It is an amenable number.

21929993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21929993 is an equidigital number, since it uses as much as digits as its factorization.

21929993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 78732, while the sum is 44.

The square root of 21929993 is about 4682.9470421947. The cubic root of 21929993 is about 279.9064015385.

It can be divided in two parts, 21929 and 993, that added together give a palindrome (22922).

The spelling of 21929993 in words is "twenty-one million, nine hundred twenty-nine thousand, nine hundred ninety-three".