21540235 has 4 divisors (see below), whose sum is σ = 25848288. Its totient is φ = 17232184.

The previous prime is 21540229. The next prime is 21540247. The reversal of 21540235 is 53204512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21540235 - 2³ = 21540227 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2154019 + ... + 2154028.

It is an arithmetic number, because the mean of its divisors is an integer number (6462072).

Almost surely, 2^21540235 is an apocalyptic number.

21540235 is a deficient number, since it is larger than the sum of its proper divisors (4308053).

21540235 is an equidigital number, since it uses as much as digits as its factorization.

21540235 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4308052.

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 21540235 is about 4641.1458714417. The cubic root of 21540235 is about 278.2382366828.

Adding to 21540235 its reverse (53204512), we get a palindrome (74744747).

The spelling of 21540235 in words is "twenty-one million, five hundred forty thousand, two hundred thirty-five".