21171655751 has 4 divisors (see below), whose sum is σ = 21178818552. Its totient is φ = 21164492952.

The previous prime is 21171655693. The next prime is 21171655753. The reversal of 21171655751 is 15755617112.

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 21171655751 - 2²⁶ = 21104546887 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21171655699 and 21171655708.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21171655753) 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, 3576965 + ... + 3582878.

It is an arithmetic number, because the mean of its divisors is an integer number (5294704638).

Almost surely, 2^21171655751 is an apocalyptic number.

21171655751 is a deficient number, since it is larger than the sum of its proper divisors (7162801).

21171655751 is an equidigital number, since it uses as much as digits as its factorization.

21171655751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7162800.

The product of its digits is 73500, while the sum is 41.

The spelling of 21171655751 in words is "twenty-one billion, one hundred seventy-one million, six hundred fifty-five thousand, seven hundred fifty-one".