9721405781 has 24 divisors (see below), whose sum is σ = 10235957160. Its totient is φ = 9231231744.

The previous prime is 9721405747. The next prime is 9721405823. The reversal of 9721405781 is 1875041279.

It can be written as a sum of positive squares in 12 ways, for example, as 1413083281 + 8308322500 = 37591^2 + 91150^2 .

It is not a de Polignac number, because 9721405781 - 2¹⁰ = 9721404757 is a prime.

It is a super-2 number, since 2×9721405781² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9721405711) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15858431 + ... + 15859043.

It is an arithmetic number, because the mean of its divisors is an integer number (426498215).

Almost surely, 2^9721405781 is an apocalyptic number.

It is an amenable number.

9721405781 is a deficient number, since it is larger than the sum of its proper divisors (514551379).

9721405781 is a wasteful number, since it uses less digits than its factorization.

9721405781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 953 (or 924 counting only the distinct ones).

The product of its (nonzero) digits is 141120, while the sum is 44.

The square root of 9721405781 is about 98597.1895187687. The cubic root of 9721405781 is about 2134.2388627761.

The spelling of 9721405781 in words is "nine billion, seven hundred twenty-one million, four hundred five thousand, seven hundred eighty-one".