21409437 has 16 divisors (see below), whose sum is σ = 33677312. Its totient is φ = 11838960.

The previous prime is 21409429. The next prime is 21409457. The reversal of 21409437 is 73490412.

It is a happy number.

It is not a de Polignac number, because 21409437 - 2³ = 21409429 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21409417) 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, 15793 + ... + 17094.

It is an arithmetic number, because the mean of its divisors is an integer number (2104832).

Almost surely, 2^21409437 is an apocalyptic number.

It is an amenable number.

21409437 is a deficient number, since it is larger than the sum of its proper divisors (12267875).

21409437 is a wasteful number, since it uses less digits than its factorization.

21409437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32928.

The product of its (nonzero) digits is 6048, while the sum is 30.

The square root of 21409437 is about 4627.0332827850. The cubic root of 21409437 is about 277.6739141945.

Adding to 21409437 its reverse (73490412), we get a palindrome (94899849).

The spelling of 21409437 in words is "twenty-one million, four hundred nine thousand, four hundred thirty-seven".