21729712 has 20 divisors (see below), whose sum is σ = 42245560. Its totient is φ = 10827648.

The previous prime is 21729709. The next prime is 21729739. The reversal of 21729712 is 21792712.

It is a happy number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 2839 + ... + 7177.

It is an arithmetic number, because the mean of its divisors is an integer number (2112278).

Almost surely, 2^21729712 is an apocalyptic number.

It is an amenable number.

21729712 is a deficient number, since it is larger than the sum of its proper divisors (20515848).

21729712 is a wasteful number, since it uses less digits than its factorization.

21729712 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4660 (or 4654 counting only the distinct ones).

The product of its digits is 3528, while the sum is 31.

The square root of 21729712 is about 4661.5139171733. The cubic root of 21729712 is about 279.0516898273.

It can be divided in two parts, 217 and 29712, that added together give a square (29929 = 173²).

The spelling of 21729712 in words is "twenty-one million, seven hundred twenty-nine thousand, seven hundred twelve".