21866139 has 16 divisors (see below), whose sum is σ = 33085440. Its totient is φ = 14266440.

The previous prime is 21866137. The next prime is 21866189. The reversal of 21866139 is 93166812.

It is not a de Polignac number, because 21866139 - 2¹ = 21866137 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21866137) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7347 + ... + 9884.

It is an arithmetic number, because the mean of its divisors is an integer number (2067840).

Almost surely, 2^21866139 is an apocalyptic number.

21866139 is a deficient number, since it is larger than the sum of its proper divisors (11219301).

21866139 is a wasteful number, since it uses less digits than its factorization.

21866139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17287 (or 17281 counting only the distinct ones).

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

The square root of 21866139 is about 4676.1243567724. The cubic root of 21866139 is about 279.6344677433.

The spelling of 21866139 in words is "twenty-one million, eight hundred sixty-six thousand, one hundred thirty-nine".