21729946509 has 48 divisors (see below), whose sum is σ = 33074376192. Its totient is φ = 13721266944.

The previous prime is 21729946501. The next prime is 21729946519. The reversal of 21729946509 is 90564992712.

21729946509 is a `hidden beast` number, since 2 + 1 + 7 + 2 + 99 + 46 + 509 = 666.

It is not a de Polignac number, because 21729946509 - 2³ = 21729946501 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21729946501) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 9500364 + ... + 9502650.

It is an arithmetic number, because the mean of its divisors is an integer number (689049504).

Almost surely, 2^21729946509 is an apocalyptic number.

It is an amenable number.

21729946509 is a deficient number, since it is larger than the sum of its proper divisors (11344429683).

21729946509 is a wasteful number, since it uses less digits than its factorization.

21729946509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2746 (or 2743 counting only the distinct ones).

The product of its (nonzero) digits is 2449440, while the sum is 54.

The spelling of 21729946509 in words is "twenty-one billion, seven hundred twenty-nine million, nine hundred forty-six thousand, five hundred nine".