21255561160661 has 8 divisors (see below), whose sum is σ = 21333031044864. Its totient is φ = 21178107910080.

The previous prime is 21255561160651. The next prime is 21255561160723. The reversal of 21255561160661 is 16606116555212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21255561160661 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 (21255561160651) 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, 1595141 + ... + 6712346.

It is an arithmetic number, because the mean of its divisors is an integer number (2666628880608).

Almost surely, 2^{21255561160661} is an apocalyptic number.

It is an amenable number.

21255561160661 is a deficient number, since it is larger than the sum of its proper divisors (77469884203).

21255561160661 is an equidigital number, since it uses as much as digits as its factorization.

21255561160661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8316811.

The product of its (nonzero) digits is 648000, while the sum is 47.

The spelling of 21255561160661 in words is "twenty-one trillion, two hundred fifty-five billion, five hundred sixty-one million, one hundred sixty thousand, six hundred sixty-one".