21971985509693 has 4 divisors (see below), whose sum is σ = 22083518431260. Its totient is φ = 21860452588128.

The previous prime is 21971985509629. The next prime is 21971985509731. The reversal of 21971985509693 is 39690558917912.

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 21616343838244 + 355641671449 = 4649338^2 + 596357^2 .

It is a cyclic number.

It is not a de Polignac number, because 21971985509693 - 2⁶ = 21971985509629 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21971985509693.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21971985502693) 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, 55766460488 + ... + 55766460881.

It is an arithmetic number, because the mean of its divisors is an integer number (5520879607815).

Almost surely, 2^{21971985509693} is an apocalyptic number.

It is an amenable number.

21971985509693 is a deficient number, since it is larger than the sum of its proper divisors (111532921567).

21971985509693 is a wasteful number, since it uses less digits than its factorization.

21971985509693 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111532921566.

The product of its (nonzero) digits is 330674400, while the sum is 74.

The spelling of 21971985509693 in words is "twenty-one trillion, nine hundred seventy-one billion, nine hundred eighty-five million, five hundred nine thousand, six hundred ninety-three".