991089751 has 4 divisors (see below), whose sum is σ = 991336104. Its totient is φ = 990843400.

The previous prime is 991089713. The next prime is 991089763. The reversal of 991089751 is 157980199.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 157980199 = 13 ⋅12152323.

It is a cyclic number.

It is not a de Polignac number, because 991089751 - 2¹⁹ = 990565463 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 991089695 and 991089704.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991089791) 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, 117040 + ... + 125221.

It is an arithmetic number, because the mean of its divisors is an integer number (247834026).

Almost surely, 2^991089751 is an apocalyptic number.

991089751 is a deficient number, since it is larger than the sum of its proper divisors (246353).

991089751 is a wasteful number, since it uses less digits than its factorization.

991089751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 246352.

The product of its (nonzero) digits is 204120, while the sum is 49.

The square root of 991089751 is about 31481.5779623576. The cubic root of 991089751 is about 997.0210516788.

The spelling of 991089751 in words is "nine hundred ninety-one million, eighty-nine thousand, seven hundred fifty-one".