21791293 has 2 divisors, whose sum is σ = 21791294. Its totient is φ = 21791292.

The previous prime is 21791291. The next prime is 21791311. The reversal of 21791293 is 39219712.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21780889 + 10404 = 4667^2 + 102^2 .

It is a cyclic number.

It is not a de Polignac number, because 21791293 - 2¹ = 21791291 is a prime.

It is a super-2 number, since 2×21791293² = 949720901223698, which contains 22 as substring.

Together with 21791291, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21791291) 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, 10895646 + 10895647.

It is an arithmetic number, because the mean of its divisors is an integer number (10895647).

Almost surely, 2^21791293 is an apocalyptic number.

It is an amenable number.

21791293 is a deficient number, since it is larger than the sum of its proper divisors (1).

21791293 is an equidigital number, since it uses as much as digits as its factorization.

21791293 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6804, while the sum is 34.

The square root of 21791293 is about 4668.1145015948. The cubic root of 21791293 is about 279.3150477350.

The spelling of 21791293 in words is "twenty-one million, seven hundred ninety-one thousand, two hundred ninety-three".