9991961 has 16 divisors (see below), whose sum is σ = 11848704. Its totient is φ = 8247744.

The previous prime is 9991939. The next prime is 9991963. The reversal of 9991961 is 1691999.

It is a happy number.

9991961 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 9991961 - 2¹⁸ = 9729817 is a prime.

It is not an unprimeable number, because it can be changed into a prime (9991963) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 44696 + ... + 44918.

It is an arithmetic number, because the mean of its divisors is an integer number (740544).

Almost surely, 2^9991961 is an apocalyptic number.

It is an amenable number.

9991961 is a deficient number, since it is larger than the sum of its proper divisors (1856743).

9991961 is a wasteful number, since it uses less digits than its factorization.

9991961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 440.

The product of its digits is 39366, while the sum is 44.

The square root of 9991961 is about 3161.0063271053. The cubic root of 9991961 is about 215.3857218579.

The spelling of 9991961 in words is "nine million, nine hundred ninety-one thousand, nine hundred sixty-one".