21791797557 has 8 divisors (see below), whose sum is σ = 30319022784. Its totient is φ = 13896218688.

The previous prime is 21791797553. The next prime is 21791797583. The reversal of 21791797557 is 75579719712.

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

It is not a de Polignac number, because 21791797557 - 2² = 21791797553 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21791797557.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21791797553) 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, 157911508 + ... + 157911645.

It is an arithmetic number, because the mean of its divisors is an integer number (3789877848).

Almost surely, 2^21791797557 is an apocalyptic number.

It is an amenable number.

21791797557 is a deficient number, since it is larger than the sum of its proper divisors (8527225227).

21791797557 is a wasteful number, since it uses less digits than its factorization.

21791797557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 315823179.

The product of its digits is 9724050, while the sum is 60.

The spelling of 21791797557 in words is "twenty-one billion, seven hundred ninety-one million, seven hundred ninety-seven thousand, five hundred fifty-seven".