21038409 has 24 divisors (see below), whose sum is σ = 34856640. Its totient is φ = 11978208.

The previous prime is 21038393. The next prime is 21038419. The reversal of 21038409 is 90483012.

It is not a de Polignac number, because 21038409 - 2⁴ = 21038393 is a prime.

It is a super-2 number, since 2×21038409² = 885229306502562, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21038419) 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, 25999 + ... + 26795.

It is an arithmetic number, because the mean of its divisors is an integer number (1452360).

Almost surely, 2^21038409 is an apocalyptic number.

It is an amenable number.

21038409 is a deficient number, since it is larger than the sum of its proper divisors (13818231).

21038409 is a wasteful number, since it uses less digits than its factorization.

21038409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1229 (or 1226 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21038409 is about 4586.7645459518. The cubic root of 21038409 is about 276.0605176054.

The spelling of 21038409 in words is "twenty-one million, thirty-eight thousand, four hundred nine".