21657012017 has 4 divisors (see below), whose sum is σ = 21676195620. Its totient is φ = 21637828416.

The previous prime is 21657012001. The next prime is 21657012019. The reversal of 21657012017 is 71021075612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7393248256 + 14263763761 = 85984^2 + 119431^2 .

It is a cyclic number.

It is not a de Polignac number, because 21657012017 - 2⁴ = 21657012001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21657012019) 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, 9590108 + ... + 9592365.

It is an arithmetic number, because the mean of its divisors is an integer number (5419048905).

Almost surely, 2^21657012017 is an apocalyptic number.

It is an amenable number.

21657012017 is a deficient number, since it is larger than the sum of its proper divisors (19183603).

21657012017 is a wasteful number, since it uses less digits than its factorization.

21657012017 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19183602.

The product of its (nonzero) digits is 5880, while the sum is 32.

Adding to 21657012017 its reverse (71021075612), we get a palindrome (92678087629).

The spelling of 21657012017 in words is "twenty-one billion, six hundred fifty-seven million, twelve thousand, seventeen".