21706128641 has 8 divisors (see below), whose sum is σ = 22124257704. Its totient is φ = 21288317440.

The previous prime is 21706128593. The next prime is 21706128659. The reversal of 21706128641 is 14682160712.

It can be written as a sum of positive squares in 4 ways, for example, as 3459792400 + 18246336241 = 58820^2 + 135079^2 .

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-21706128641 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21706128595 and 21706128604.

It is not an unprimeable number, because it can be changed into a prime (21706124641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 60785 + ... + 217041.

It is an arithmetic number, because the mean of its divisors is an integer number (2765532213).

Almost surely, 2^21706128641 is an apocalyptic number.

It is an amenable number.

21706128641 is a deficient number, since it is larger than the sum of its proper divisors (418129063).

21706128641 is a wasteful number, since it uses less digits than its factorization.

21706128641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158931.

The product of its (nonzero) digits is 32256, while the sum is 38.

The spelling of 21706128641 in words is "twenty-one billion, seven hundred six million, one hundred twenty-eight thousand, six hundred forty-one".