21729331 has 8 divisors (see below), whose sum is σ = 24632720. Its totient is φ = 19001952.

The previous prime is 21729329. The next prime is 21729341. The reversal of 21729331 is 13392712.

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 21729331 - 2¹ = 21729329 is a prime.

It is a super-2 number, since 2×21729331² = 944327651415122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21729331.

It is not an unprimeable number, because it can be changed into a prime (21729341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43740 + ... + 44233.

It is an arithmetic number, because the mean of its divisors is an integer number (3079090).

Almost surely, 2^21729331 is an apocalyptic number.

21729331 is a deficient number, since it is larger than the sum of its proper divisors (2903389).

21729331 is a wasteful number, since it uses less digits than its factorization.

21729331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 88005.

The product of its digits is 2268, while the sum is 28.

The square root of 21729331 is about 4661.4730504423. The cubic root of 21729331 is about 279.0500588912.

The spelling of 21729331 in words is "twenty-one million, seven hundred twenty-nine thousand, three hundred thirty-one".