21492309 has 8 divisors (see below), whose sum is σ = 28822752. Its totient is φ = 14245040.

The previous prime is 21492259. The next prime is 21492349. The reversal of 21492309 is 90329412.

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

It is a cyclic number.

It is not a de Polignac number, because 21492309 - 2¹⁶ = 21426773 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21492349) 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, 20187 + ... + 21224.

It is an arithmetic number, because the mean of its divisors is an integer number (3602844).

Almost surely, 2^21492309 is an apocalyptic number.

It is an amenable number.

21492309 is a deficient number, since it is larger than the sum of its proper divisors (7330443).

21492309 is a wasteful number, since it uses less digits than its factorization.

21492309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41587.

The product of its (nonzero) digits is 3888, while the sum is 30.

The square root of 21492309 is about 4635.9798317076. The cubic root of 21492309 is about 278.0317278282.

The spelling of 21492309 in words is "twenty-one million, four hundred ninety-two thousand, three hundred nine".