21660329 has 4 divisors (see below), whose sum is σ = 22934484. Its totient is φ = 20386176.

The previous prime is 21660311. The next prime is 21660367. The reversal of 21660329 is 92306612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13337104 + 8323225 = 3652^2 + 2885^2 .

It is a cyclic number.

It is not a de Polignac number, because 21660329 - 2¹² = 21656233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21660389) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 637052 + ... + 637085.

It is an arithmetic number, because the mean of its divisors is an integer number (5733621).

Almost surely, 2^21660329 is an apocalyptic number.

It is an amenable number.

21660329 is a deficient number, since it is larger than the sum of its proper divisors (1274155).

21660329 is a wasteful number, since it uses less digits than its factorization.

21660329 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1274154.

The product of its (nonzero) digits is 3888, while the sum is 29.

The square root of 21660329 is about 4654.0658568611. The cubic root of 21660329 is about 278.7543690119.

The spelling of 21660329 in words is "twenty-one million, six hundred sixty thousand, three hundred twenty-nine".