21255210155 has 4 divisors (see below), whose sum is σ = 25506252192. Its totient is φ = 17004168120.

The previous prime is 21255210121. The next prime is 21255210167. The reversal of 21255210155 is 55101255212.

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

It is not a de Polignac number, because 21255210155 - 2³⁰ = 20181468331 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, 2125521011 + ... + 2125521020.

It is an arithmetic number, because the mean of its divisors is an integer number (6376563048).

Almost surely, 2^21255210155 is an apocalyptic number.

21255210155 is a deficient number, since it is larger than the sum of its proper divisors (4251042037).

21255210155 is an equidigital number, since it uses as much as digits as its factorization.

21255210155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4251042036.

The product of its (nonzero) digits is 5000, while the sum is 29.

Adding to 21255210155 its reverse (55101255212), we get a palindrome (76356465367).

The spelling of 21255210155 in words is "twenty-one billion, two hundred fifty-five million, two hundred ten thousand, one hundred fifty-five".