21621455055451 has 4 divisors (see below), whose sum is σ = 21707596310904. Its totient is φ = 21535313800000.

The previous prime is 21621455055413. The next prime is 21621455055481. The reversal of 21621455055451 is 15455055412612.

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 21621455055451 - 2⁷ = 21621455055323 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21621455055481) 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 3 ways as a sum of consecutive naturals, for example, 43070627350 + ... + 43070627851.

It is an arithmetic number, because the mean of its divisors is an integer number (5426899077726).

Almost surely, 2^{21621455055451} is an apocalyptic number.

21621455055451 is a deficient number, since it is larger than the sum of its proper divisors (86141255453).

21621455055451 is an equidigital number, since it uses as much as digits as its factorization.

21621455055451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86141255452.

The product of its (nonzero) digits is 1200000, while the sum is 46.

The spelling of 21621455055451 in words is "twenty-one trillion, six hundred twenty-one billion, four hundred fifty-five million, fifty-five thousand, four hundred fifty-one".