21951778729 has 8 divisors (see below), whose sum is σ = 22625312328. Its totient is φ = 21282468480.

The previous prime is 21951778699. The next prime is 21951778747. The reversal of 21951778729 is 92787715912.

It can be written as a sum of positive squares in 4 ways, for example, as 7629673104 + 14322105625 = 87348^2 + 119675^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21951778729 - 2⁵ = 21951778697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21951773729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1045282 + ... + 1066075.

It is an arithmetic number, because the mean of its divisors is an integer number (2828164041).

Almost surely, 2^21951778729 is an apocalyptic number.

It is an amenable number.

21951778729 is a deficient number, since it is larger than the sum of its proper divisors (673533599).

21951778729 is a wasteful number, since it uses less digits than its factorization.

21951778729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2111675.

The product of its digits is 4445280, while the sum is 58.

The spelling of 21951778729 in words is "twenty-one billion, nine hundred fifty-one million, seven hundred seventy-eight thousand, seven hundred twenty-nine".