21550120451 has 4 divisors (see below), whose sum is σ = 21550576152. Its totient is φ = 21549664752.

The previous prime is 21550120399. The next prime is 21550120483. The reversal of 21550120451 is 15402105512.

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

It is a cyclic number.

It is not a de Polignac number, because 21550120451 - 2⁶ = 21550120387 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 21550120451.

It is not an unprimeable number, because it can be changed into a prime (21550120651) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 147461 + ... + 254646.

It is an arithmetic number, because the mean of its divisors is an integer number (5387644038).

Almost surely, 2^21550120451 is an apocalyptic number.

21550120451 is a deficient number, since it is larger than the sum of its proper divisors (455701).

21550120451 is an equidigital number, since it uses as much as digits as its factorization.

21550120451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 455700.

The product of its (nonzero) digits is 2000, while the sum is 26.

Adding to 21550120451 its reverse (15402105512), we get a palindrome (36952225963).

The spelling of 21550120451 in words is "twenty-one billion, five hundred fifty million, one hundred twenty thousand, four hundred fifty-one".