21729159 has 12 divisors (see below), whose sum is σ = 31617456. Its totient is φ = 14379552.

The previous prime is 21729143. The next prime is 21729161. The reversal of 21729159 is 95192712.

It is not a de Polignac number, because 21729159 - 2⁴ = 21729143 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21729119) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7579 + ... + 10044.

It is an arithmetic number, because the mean of its divisors is an integer number (2634788).

Almost surely, 2^21729159 is an apocalyptic number.

21729159 is a deficient number, since it is larger than the sum of its proper divisors (9888297).

21729159 is a wasteful number, since it uses less digits than its factorization.

21729159 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17766 (or 17763 counting only the distinct ones).

The product of its digits is 11340, while the sum is 36.

The square root of 21729159 is about 4661.4546013020. The cubic root of 21729159 is about 279.0493226093.

The spelling of 21729159 in words is "twenty-one million, seven hundred twenty-nine thousand, one hundred fifty-nine".