21135699685 has 4 divisors (see below), whose sum is σ = 25362839628. Its totient is φ = 16908559744.

The previous prime is 21135699659. The next prime is 21135699691. The reversal of 21135699685 is 58699653112.

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 11286725121 + 9848974564 = 106239^2 + 99242^2 .

It is a cyclic number.

It is not a de Polignac number, because 21135699685 - 2¹¹ = 21135697637 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2113569964 + ... + 2113569973.

It is an arithmetic number, because the mean of its divisors is an integer number (6340709907).

Almost surely, 2^21135699685 is an apocalyptic number.

It is an amenable number.

21135699685 is a deficient number, since it is larger than the sum of its proper divisors (4227139943).

21135699685 is an equidigital number, since it uses as much as digits as its factorization.

21135699685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4227139942.

The product of its digits is 3499200, while the sum is 55.

The spelling of 21135699685 in words is "twenty-one billion, one hundred thirty-five million, six hundred ninety-nine thousand, six hundred eighty-five".