21729316 has 12 divisors (see below), whose sum is σ = 43458688. Its totient is φ = 9312552.

The previous prime is 21729313. The next prime is 21729329. The reversal of 21729316 is 61392712.

21729316 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21729313) 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, 387996 + ... + 388051.

Almost surely, 2^21729316 is an apocalyptic number.

It is an amenable number.

21729316 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21729316 is a wasteful number, since it uses less digits than its factorization.

21729316 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 776058 (or 776056 counting only the distinct ones).

The product of its digits is 4536, while the sum is 31.

The square root of 21729316 is about 4661.4714415086. The cubic root of 21729316 is about 279.0499946807.

The spelling of 21729316 in words is "twenty-one million, seven hundred twenty-nine thousand, three hundred sixteen".