21377613685 has 4 divisors (see below), whose sum is σ = 25653136428. Its totient is φ = 17102090944.

The previous prime is 21377613667. The next prime is 21377613743. The reversal of 21377613685 is 58631677312.

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 7470836356 + 13906777329 = 86434^2 + 117927^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21377613685 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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, 2137761364 + ... + 2137761373.

It is an arithmetic number, because the mean of its divisors is an integer number (6413284107).

Almost surely, 2^21377613685 is an apocalyptic number.

It is an amenable number.

21377613685 is a deficient number, since it is larger than the sum of its proper divisors (4275522743).

21377613685 is an equidigital number, since it uses as much as digits as its factorization.

21377613685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4275522742.

The product of its digits is 1270080, while the sum is 49.

The spelling of 21377613685 in words is "twenty-one billion, three hundred seventy-seven million, six hundred thirteen thousand, six hundred eighty-five".