21868137 has 20 divisors (see below), whose sum is σ = 34590996. Its totient is φ = 13720320.

The previous prime is 21868127. The next prime is 21868139. The reversal of 21868137 is 73186812.

It can be written as a sum of positive squares in 2 ways, for example, as 18974736 + 2893401 = 4356^2 + 1701^2 .

It is not a de Polignac number, because 21868137 - 2¹⁰ = 21867113 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21868139) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 6564 + ... + 9317.

Almost surely, 2^21868137 is an apocalyptic number.

21868137 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21868137 is a deficient number, since it is larger than the sum of its proper divisors (12722859).

21868137 is a wasteful number, since it uses less digits than its factorization.

21868137 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15910 (or 15901 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 21868137 is about 4676.3379903510. The cubic root of 21868137 is about 279.6429846051.

The spelling of 21868137 in words is "twenty-one million, eight hundred sixty-eight thousand, one hundred thirty-seven".