21521102455 has 4 divisors (see below), whose sum is σ = 25825322952. Its totient is φ = 17216881960.

The previous prime is 21521102423. The next prime is 21521102489. The reversal of 21521102455 is 55420112512.

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

It is not a de Polignac number, because 21521102455 - 2⁵ = 21521102423 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, 2152110241 + ... + 2152110250.

It is an arithmetic number, because the mean of its divisors is an integer number (6456330738).

Almost surely, 2^21521102455 is an apocalyptic number.

21521102455 is a deficient number, since it is larger than the sum of its proper divisors (4304220497).

21521102455 is an equidigital number, since it uses as much as digits as its factorization.

21521102455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4304220496.

The product of its (nonzero) digits is 4000, while the sum is 28.

Adding to 21521102455 its reverse (55420112512), we get a palindrome (76941214967).

The spelling of 21521102455 in words is "twenty-one billion, five hundred twenty-one million, one hundred two thousand, four hundred fifty-five".