21690837 has 24 divisors (see below), whose sum is σ = 37693760. Its totient is φ = 11741760.

The previous prime is 21690821. The next prime is 21690853. The reversal of 21690837 is 73809612.

It is an interprime number because it is at equal distance from previous prime (21690821) and next prime (21690853).

It is not a de Polignac number, because 21690837 - 2⁴ = 21690821 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690857) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7864 + ... + 10257.

Almost surely, 2^21690837 is an apocalyptic number.

It is an amenable number.

21690837 is a deficient number, since it is larger than the sum of its proper divisors (16002923).

21690837 is a wasteful number, since it uses less digits than its factorization.

21690837 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18153 (or 18150 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21690837 is about 4657.3422678605. The cubic root of 21690837 is about 278.8851803329.

The spelling of 21690837 in words is "twenty-one million, six hundred ninety thousand, eight hundred thirty-seven".