21729242099 has 4 divisors (see below), whose sum is σ = 22872886440. Its totient is φ = 20585597760.

The previous prime is 21729242071. The next prime is 21729242167. The reversal of 21729242099 is 99024292712.

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

It is a cyclic number.

It is not a de Polignac number, because 21729242099 - 2¹⁶ = 21729176563 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21729242039) 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, 571822142 + ... + 571822179.

It is an arithmetic number, because the mean of its divisors is an integer number (5718221610).

Almost surely, 2^21729242099 is an apocalyptic number.

21729242099 is a deficient number, since it is larger than the sum of its proper divisors (1143644341).

21729242099 is a wasteful number, since it uses less digits than its factorization.

21729242099 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1143644340.

The product of its (nonzero) digits is 326592, while the sum is 47.

The spelling of 21729242099 in words is "twenty-one billion, seven hundred twenty-nine million, two hundred forty-two thousand, ninety-nine".