21399793 has 2 divisors, whose sum is σ = 21399794. Its totient is φ = 21399792.

The previous prime is 21399773. The next prime is 21399797. The reversal of 21399793 is 39799312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16875664 + 4524129 = 4108^2 + 2127^2 .

It is a cyclic number.

It is not a de Polignac number, because 21399793 - 2⁵ = 21399761 is a prime.

It is a super-2 number, since 2×21399793² = 915902280885698, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21399797) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10699896 + 10699897.

It is an arithmetic number, because the mean of its divisors is an integer number (10699897).

Almost surely, 2^21399793 is an apocalyptic number.

It is an amenable number.

21399793 is a deficient number, since it is larger than the sum of its proper divisors (1).

21399793 is an equidigital number, since it uses as much as digits as its factorization.

21399793 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 91854, while the sum is 43.

The square root of 21399793 is about 4625.9910289580. The cubic root of 21399793 is about 277.6322146795.

The spelling of 21399793 in words is "twenty-one million, three hundred ninety-nine thousand, seven hundred ninety-three".