21761255 has 4 divisors (see below), whose sum is σ = 26113512. Its totient is φ = 17409000.

The previous prime is 21761249. The next prime is 21761279. The reversal of 21761255 is 55216712.

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

It is not a de Polignac number, because 21761255 - 2⁴ = 21761239 is a prime.

It is a Duffinian number.

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, 2176121 + ... + 2176130.

It is an arithmetic number, because the mean of its divisors is an integer number (6528378).

Almost surely, 2^21761255 is an apocalyptic number.

21761255 is a deficient number, since it is larger than the sum of its proper divisors (4352257).

21761255 is an equidigital number, since it uses as much as digits as its factorization.

21761255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4352256.

The product of its digits is 4200, while the sum is 29.

The square root of 21761255 is about 4664.8960331394. The cubic root of 21761255 is about 279.1866489991.

Adding to 21761255 its reverse (55216712), we get a palindrome (76977967).

The spelling of 21761255 in words is "twenty-one million, seven hundred sixty-one thousand, two hundred fifty-five".