21172329 has 6 divisors (see below), whose sum is σ = 30582266. Its totient is φ = 14114880.

The previous prime is 21172309. The next prime is 21172331. The reversal of 21172329 is 92327112.

It can be written as a sum of positive squares in only one way, i.e., 12616704 + 8555625 = 3552^2 + 2925^2 .

It is not a de Polignac number, because 21172329 - 2²³ = 12783721 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 (21172309) 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, 1176232 + ... + 1176249.

Almost surely, 2^21172329 is an apocalyptic number.

It is an amenable number.

21172329 is a deficient number, since it is larger than the sum of its proper divisors (9409937).

21172329 is a wasteful number, since it uses less digits than its factorization.

21172329 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2352487 (or 2352484 counting only the distinct ones).

The product of its digits is 1512, while the sum is 27.

The square root of 21172329 is about 4601.3399135469. The cubic root of 21172329 is about 276.6450335499.

The spelling of 21172329 in words is "twenty-one million, one hundred seventy-two thousand, three hundred twenty-nine".