21497799857 has 8 divisors (see below), whose sum is σ = 22037154120. Its totient is φ = 20965063680.

The previous prime is 21497799811. The next prime is 21497799877. The reversal of 21497799857 is 75899779412.

It can be written as a sum of positive squares in 4 ways, for example, as 6767365696 + 14730434161 = 82264^2 + 121369^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21497799857 - 2¹⁸ = 21497537713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21497799877) 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, 1647944 + ... + 1660937.

It is an arithmetic number, because the mean of its divisors is an integer number (2754644265).

Almost surely, 2^21497799857 is an apocalyptic number.

It is an amenable number.

21497799857 is a deficient number, since it is larger than the sum of its proper divisors (539354263).

21497799857 is an equidigital number, since it uses as much as digits as its factorization.

21497799857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3309043.

The product of its digits is 80015040, while the sum is 68.

The spelling of 21497799857 in words is "twenty-one billion, four hundred ninety-seven million, seven hundred ninety-nine thousand, eight hundred fifty-seven".