21540393 has 12 divisors (see below), whose sum is σ = 35558848. Its totient is φ = 12308760.

The previous prime is 21540383. The next prime is 21540437. The reversal of 21540393 is 39304512.

It is not a de Polignac number, because 21540393 - 2⁵ = 21540361 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540383) 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 in 11 ways as a sum of consecutive naturals, for example, 170893 + ... + 171018.

Almost surely, 2^21540393 is an apocalyptic number.

It is an amenable number.

21540393 is a deficient number, since it is larger than the sum of its proper divisors (14018455).

21540393 is a wasteful number, since it uses less digits than its factorization.

21540393 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 341924 (or 341921 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 27.

The square root of 21540393 is about 4641.1628930689. The cubic root of 21540393 is about 278.2389169838.

It can be divided in two parts, 215403 and 93, that added together give a triangular number (215496 = T₆₅₆).

The spelling of 21540393 in words is "twenty-one million, five hundred forty thousand, three hundred ninety-three".