21192409 has 4 divisors (see below), whose sum is σ = 24219904. Its totient is φ = 18164916.

The previous prime is 21192403. The next prime is 21192427. The reversal of 21192409 is 90429112.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21192409 - 2¹³ = 21184217 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21192403) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1513737 + ... + 1513750.

It is an arithmetic number, because the mean of its divisors is an integer number (6054976).

Almost surely, 2^21192409 is an apocalyptic number.

It is an amenable number.

21192409 is a deficient number, since it is larger than the sum of its proper divisors (3027495).

21192409 is an equidigital number, since it uses as much as digits as its factorization.

21192409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3027494.

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 21192409 is about 4603.5213695605. The cubic root of 21192409 is about 276.7324633433.

The spelling of 21192409 in words is "twenty-one million, one hundred ninety-two thousand, four hundred nine".