21408937 has 16 divisors (see below), whose sum is σ = 23950080. Its totient is φ = 18974800.

The previous prime is 21408913. The next prime is 21408943. The reversal of 21408937 is 73980412.

It is a cyclic number.

It is not a de Polignac number, because 21408937 - 2¹⁹ = 20884649 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21400937) 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, 119514 + ... + 119692.

It is an arithmetic number, because the mean of its divisors is an integer number (1496880).

Almost surely, 2^21408937 is an apocalyptic number.

It is an amenable number.

21408937 is a deficient number, since it is larger than the sum of its proper divisors (2541143).

21408937 is a wasteful number, since it uses less digits than its factorization.

21408937 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 21408937 is about 4626.9792521687. The cubic root of 21408937 is about 277.6717525615.

The spelling of 21408937 in words is "twenty-one million, four hundred eight thousand, nine hundred thirty-seven".