21686193 has 12 divisors (see below), whose sum is σ = 31648708. Its totient is φ = 14307840.

The previous prime is 21686177. The next prime is 21686207. The reversal of 21686193 is 39168612.

It can be written as a sum of positive squares in 2 ways, for example, as 4941729 + 16744464 = 2223^2 + 4092^2 .

It is not a de Polignac number, because 21686193 - 2⁴ = 21686177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21686123) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11548 + ... + 13293.

Almost surely, 2^21686193 is an apocalyptic number.

It is an amenable number.

21686193 is a deficient number, since it is larger than the sum of its proper divisors (9962515).

21686193 is a wasteful number, since it uses less digits than its factorization.

21686193 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24944 (or 24941 counting only the distinct ones).

The product of its digits is 15552, while the sum is 36.

The square root of 21686193 is about 4656.8436735626. The cubic root of 21686193 is about 278.8652758418.

The spelling of 21686193 in words is "twenty-one million, six hundred eighty-six thousand, one hundred ninety-three".