21150451555 has 4 divisors (see below), whose sum is σ = 25380541872. Its totient is φ = 16920361240.

The previous prime is 21150451523. The next prime is 21150451579. The reversal of 21150451555 is 55515405112.

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

It is not a de Polignac number, because 21150451555 - 2⁵ = 21150451523 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 21150451555.

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, 2115045151 + ... + 2115045160.

It is an arithmetic number, because the mean of its divisors is an integer number (6345135468).

Almost surely, 2^21150451555 is an apocalyptic number.

21150451555 is a deficient number, since it is larger than the sum of its proper divisors (4230090317).

21150451555 is an equidigital number, since it uses as much as digits as its factorization.

21150451555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4230090316.

The product of its (nonzero) digits is 25000, while the sum is 34.

Adding to 21150451555 its reverse (55515405112), we get a palindrome (76665856667).

The spelling of 21150451555 in words is "twenty-one billion, one hundred fifty million, four hundred fifty-one thousand, five hundred fifty-five".