21173006826551 has 4 divisors (see below), whose sum is σ = 21173033343504. Its totient is φ = 21172980309600.

The previous prime is 21173006826529. The next prime is 21173006826557. The reversal of 21173006826551 is 15562860037112.

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 21173006826551 - 2³⁴ = 21155826957367 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21173006826496 and 21173006826505.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21173006826557) 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, 12022355 + ... + 13670516.

It is an arithmetic number, because the mean of its divisors is an integer number (5293258335876).

Almost surely, 2^{21173006826551} is an apocalyptic number.

21173006826551 is a deficient number, since it is larger than the sum of its proper divisors (26516953).

21173006826551 is an equidigital number, since it uses as much as digits as its factorization.

21173006826551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26516952.

The product of its (nonzero) digits is 604800, while the sum is 47.

The spelling of 21173006826551 in words is "twenty-one trillion, one hundred seventy-three billion, six million, eight hundred twenty-six thousand, five hundred fifty-one".