21240455 has 4 divisors (see below), whose sum is σ = 25488552. Its totient is φ = 16992360.

The previous prime is 21240433. The next prime is 21240511. The reversal of 21240455 is 55404212.

It is a happy number.

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

It is not a de Polignac number, because 21240455 - 2⁶ = 21240391 is a prime.

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 21240455.

It is a congruent 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, 2124041 + ... + 2124050.

It is an arithmetic number, because the mean of its divisors is an integer number (6372138).

Almost surely, 2^21240455 is an apocalyptic number.

21240455 is a deficient number, since it is larger than the sum of its proper divisors (4248097).

21240455 is an equidigital number, since it uses as much as digits as its factorization.

21240455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4248096.

The product of its (nonzero) digits is 1600, while the sum is 23.

The square root of 21240455 is about 4608.7368117522. The cubic root of 21240455 is about 276.9414352244.

Adding to 21240455 its reverse (55404212), we get a palindrome (76644667).

The spelling of 21240455 in words is "twenty-one million, two hundred forty thousand, four hundred fifty-five".