9961645381 has 2 divisors, whose sum is σ = 9961645382. Its totient is φ = 9961645380.

The previous prime is 9961645349. The next prime is 9961645403. The reversal of 9961645381 is 1835461699.

9961645381 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9203524225 + 758121156 = 95935^2 + 27534^2 .

It is an emirp because it is prime and its reverse (1835461699) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9961645381 - 2⁵ = 9961645349 is a prime.

It is a super-2 number, since 2×9961645381² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9961945381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4980822690 + 4980822691.

It is an arithmetic number, because the mean of its divisors is an integer number (4980822691).

Almost surely, 2^9961645381 is an apocalyptic number.

It is an amenable number.

9961645381 is a deficient number, since it is larger than the sum of its proper divisors (1).

9961645381 is an equidigital number, since it uses as much as digits as its factorization.

9961645381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1399680, while the sum is 52.

The square root of 9961645381 is about 99808.0426669114. The cubic root of 9961645381 is about 2151.6767436315.

The spelling of 9961645381 in words is "nine billion, nine hundred sixty-one million, six hundred forty-five thousand, three hundred eighty-one".