21321243 has 12 divisors (see below), whose sum is σ = 31320120. Its totient is φ = 13972896.

The previous prime is 21321217. The next prime is 21321263. The reversal of 21321243 is 34212312.

It is not a de Polignac number, because 21321243 - 2⁸ = 21320987 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21321203) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19546 + ... + 20607.

It is an arithmetic number, because the mean of its divisors is an integer number (2610010).

Almost surely, 2^21321243 is an apocalyptic number.

21321243 is a deficient number, since it is larger than the sum of its proper divisors (9998877).

21321243 is a wasteful number, since it uses less digits than its factorization.

21321243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40218 (or 40215 counting only the distinct ones).

The product of its digits is 288, while the sum is 18.

The square root of 21321243 is about 4617.4931510507. The cubic root of 21321243 is about 277.2921062836.

Adding to 21321243 its reverse (34212312), we get a palindrome (55533555).

It can be divided in two parts, 2132 and 1243, that added together give a cube (3375 = 15³).

The spelling of 21321243 in words is "twenty-one million, three hundred twenty-one thousand, two hundred forty-three".