21689437 has 32 divisors (see below), whose sum is σ = 29067264. Its totient is φ = 15681600.

The previous prime is 21689413. The next prime is 21689449. The reversal of 21689437 is 73498612.

It is not a de Polignac number, because 21689437 - 2⁷ = 21689309 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21689437.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21689407) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 65362 + ... + 65692.

It is an arithmetic number, because the mean of its divisors is an integer number (908352).

It is a vampire number, since it can be written as 2849 ⋅ 7613 (with its own digits).

Almost surely, 2^21689437 is an apocalyptic number.

It is an amenable number.

21689437 is a deficient number, since it is larger than the sum of its proper divisors (7377827).

21689437 is a wasteful number, since it uses less digits than its factorization.

21689437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 409.

The product of its digits is 72576, while the sum is 40.

The square root of 21689437 is about 4657.1919651223. The cubic root of 21689437 is about 278.8791801395.

The spelling of 21689437 in words is "twenty-one million, six hundred eighty-nine thousand, four hundred thirty-seven".