21390609 has 8 divisors (see below), whose sum is σ = 28545472. Its totient is φ = 14248080.

The previous prime is 21390601. The next prime is 21390613. The reversal of 21390609 is 90609312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21390609 - 2³ = 21390601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21390601) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2319 + ... + 6939.

It is an arithmetic number, because the mean of its divisors is an integer number (3568184).

Almost surely, 2^21390609 is an apocalyptic number.

It is an amenable number.

21390609 is a deficient number, since it is larger than the sum of its proper divisors (7154863).

21390609 is a wasteful number, since it uses less digits than its factorization.

21390609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6167.

The product of its (nonzero) digits is 2916, while the sum is 30.

The square root of 21390609 is about 4624.9982702699. The cubic root of 21390609 is about 277.5924925024.

The spelling of 21390609 in words is "twenty-one million, three hundred ninety thousand, six hundred nine".