21042451055551 has 8 divisors (see below), whose sum is σ = 21066916440960. Its totient is φ = 21017987107992.

The previous prime is 21042451055513. The next prime is 21042451055623. The reversal of 21042451055551 is 15555015424012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21042451055551 - 2⁹ = 21042451055039 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042451055501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30460110 + ... + 31143268.

It is an arithmetic number, because the mean of its divisors is an integer number (2633364555120).

Almost surely, 2^{21042451055551} is an apocalyptic number.

21042451055551 is a deficient number, since it is larger than the sum of its proper divisors (24465385409).

21042451055551 is an equidigital number, since it uses as much as digits as its factorization.

21042451055551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 718925.

The product of its (nonzero) digits is 200000, while the sum is 40.

Adding to 21042451055551 its reverse (15555015424012), we get a palindrome (36597466479563).

The spelling of 21042451055551 in words is "twenty-one trillion, forty-two billion, four hundred fifty-one million, fifty-five thousand, five hundred fifty-one".