9651991 has 4 divisors (see below), whose sum is σ = 9676000. Its totient is φ = 9627984.

The previous prime is 9651979. The next prime is 9652007. The reversal of 9651991 is 1991569.

9651991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1991569 = 137 ⋅14537.

It is a cyclic number.

It is not a de Polignac number, because 9651991 - 2⁵ = 9651959 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9651911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11391 + ... + 12208.

It is an arithmetic number, because the mean of its divisors is an integer number (2419000).

Almost surely, 2^9651991 is an apocalyptic number.

9651991 is a deficient number, since it is larger than the sum of its proper divisors (24009).

9651991 is a wasteful number, since it uses less digits than its factorization.

9651991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24008.

The product of its digits is 21870, while the sum is 40.

The square root of 9651991 is about 3106.7653596627. The cubic root of 9651991 is about 212.9146946933.

The spelling of 9651991 in words is "nine million, six hundred fifty-one thousand, nine hundred ninety-one".