21309045 has 8 divisors (see below), whose sum is σ = 34094496. Its totient is φ = 11364816.

The previous prime is 21309023. The next prime is 21309061. The reversal of 21309045 is 54090312.

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

It is not a de Polignac number, because 21309045 - 2⁶ = 21308981 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 710287 + ... + 710316.

It is an arithmetic number, because the mean of its divisors is an integer number (4261812).

Almost surely, 2^21309045 is an apocalyptic number.

It is an amenable number.

21309045 is a deficient number, since it is larger than the sum of its proper divisors (12785451).

21309045 is a wasteful number, since it uses less digits than its factorization.

21309045 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1420611.

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 21309045 is about 4616.1721155087. The cubic root of 21309045 is about 277.2392160847.

Adding to 21309045 its reverse (54090312), we get a palindrome (75399357).

It can be divided in two parts, 2130 and 9045, that added together give a triangular number (11175 = T₁₄₉).

The spelling of 21309045 in words is "twenty-one million, three hundred nine thousand, forty-five".