21931293 has 4 divisors (see below), whose sum is σ = 29241728. Its totient is φ = 14620860.

The previous prime is 21931289. The next prime is 21931297. The reversal of 21931293 is 39213912.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (21931289) and next prime (21931297).

It is not a de Polignac number, because 21931293 - 2² = 21931289 is a prime.

It is a super-2 number, since 2×21931293² = 961963225303698, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21931293.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21931297) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3655213 + ... + 3655218.

It is an arithmetic number, because the mean of its divisors is an integer number (7310432).

Almost surely, 2^21931293 is an apocalyptic number.

It is an amenable number.

21931293 is a deficient number, since it is larger than the sum of its proper divisors (7310435).

21931293 is an equidigital number, since it uses as much as digits as its factorization.

21931293 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7310434.

The product of its digits is 2916, while the sum is 30.

The square root of 21931293 is about 4683.0858416220. The cubic root of 21931293 is about 279.9119323372.

It can be divided in two parts, 2193 and 1293, that added together give a triangular number (3486 = T₈₃).

The spelling of 21931293 in words is "twenty-one million, nine hundred thirty-one thousand, two hundred ninety-three".