21788785729 has 8 divisors (see below), whose sum is σ = 22025251080. Its totient is φ = 21552562176.

The previous prime is 21788785703. The next prime is 21788785751. The reversal of 21788785729 is 92758788712.

It can be written as a sum of positive squares in 4 ways, for example, as 106812225 + 21681973504 = 10335^2 + 147248^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21788785729 is a prime.

It is a super-2 number, since 2×21788785729² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21788788729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 123777 + ... + 242689.

It is an arithmetic number, because the mean of its divisors is an integer number (2753156385).

Almost surely, 2^21788785729 is an apocalyptic number.

It is an amenable number.

21788785729 is a deficient number, since it is larger than the sum of its proper divisors (236465351).

21788785729 is a wasteful number, since it uses less digits than its factorization.

21788785729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120899.

The product of its digits is 31610880, while the sum is 64.

The spelling of 21788785729 in words is "twenty-one billion, seven hundred eighty-eight million, seven hundred eighty-five thousand, seven hundred twenty-nine".