21154309 has 6 divisors (see below), whose sum is σ = 23252390. Its totient is φ = 19231080.

The previous prime is 21154283. The next prime is 21154339. The reversal of 21154309 is 90345112.

It can be written as a sum of positive squares in only one way, i.e., 19554084 + 1600225 = 4422^2 + 1265^2 .

It is not a de Polignac number, because 21154309 - 2¹⁹ = 20630021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21154339) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 87294 + ... + 87535.

Almost surely, 2^21154309 is an apocalyptic number.

It is an amenable number.

21154309 is a deficient number, since it is larger than the sum of its proper divisors (2098081).

21154309 is a wasteful number, since it uses less digits than its factorization.

21154309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 174851 (or 174840 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 21154309 is about 4599.3813714455. The cubic root of 21154309 is about 276.5665260716.

The spelling of 21154309 in words is "twenty-one million, one hundred fifty-four thousand, three hundred nine".