21317383432661 has 4 divisors (see below), whose sum is σ = 22571347164012. Its totient is φ = 20063419701312.

The previous prime is 21317383432649. The next prime is 21317383432673. The reversal of 21317383432661 is 16623438371312.

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

It is an interprime number because it is at equal distance from previous prime (21317383432649) and next prime (21317383432673).

It can be written as a sum of positive squares in 2 ways, for example, as 11201866792561 + 10115516640100 = 3346919^2 + 3180490^2 .

It is a cyclic number.

It is not a de Polignac number, because 21317383432661 - 2²² = 21317379238357 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 (21317383432621) 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, 626981865650 + ... + 626981865683.

It is an arithmetic number, because the mean of its divisors is an integer number (5642836791003).

Almost surely, 2^{21317383432661} is an apocalyptic number.

It is an amenable number.

21317383432661 is a deficient number, since it is larger than the sum of its proper divisors (1253963731351).

21317383432661 is a wasteful number, since it uses less digits than its factorization.

21317383432661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1253963731350.

The product of its digits is 2612736, while the sum is 50.

The spelling of 21317383432661 in words is "twenty-one trillion, three hundred seventeen billion, three hundred eighty-three million, four hundred thirty-two thousand, six hundred sixty-one".