31128761 has 4 divisors (see below), whose sum is σ = 31419792. Its totient is φ = 30837732.

The previous prime is 31128749. The next prime is 31128787. The reversal of 31128761 is 16782113.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16782113 = 2677 ⋅6269.

It is a cyclic number.

It is not a de Polignac number, because 31128761 - 2¹⁰ = 31127737 is a prime.

It is a super-2 number, since 2×31128761² = 1937999522790242, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (31128701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 145355 + ... + 145568.

It is an arithmetic number, because the mean of its divisors is an integer number (7854948).

Almost surely, 2^31128761 is an apocalyptic number.

It is an amenable number.

31128761 is a deficient number, since it is larger than the sum of its proper divisors (291031).

31128761 is a wasteful number, since it uses less digits than its factorization.

31128761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291030.

The product of its digits is 2016, while the sum is 29.

The square root of 31128761 is about 5579.3154598033. The cubic root of 31128761 is about 314.5723970449.

The spelling of 31128761 in words is "thirty-one million, one hundred twenty-eight thousand, seven hundred sixty-one".