31440781 has 4 divisors (see below), whose sum is σ = 31719132. Its totient is φ = 31162432.

The previous prime is 31440757. The next prime is 31440811. The reversal of 31440781 is 18704413.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9030025 + 22410756 = 3005^2 + 4734^2 .

It is a cyclic number.

It is not a de Polignac number, because 31440781 - 2⁵ = 31440749 is a prime.

It is a super-2 number, since 2×31440781² = 1977045419779922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31440751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 139006 + ... + 139231.

It is an arithmetic number, because the mean of its divisors is an integer number (7929783).

Almost surely, 2^31440781 is an apocalyptic number.

It is an amenable number.

31440781 is a deficient number, since it is larger than the sum of its proper divisors (278351).

31440781 is a wasteful number, since it uses less digits than its factorization.

31440781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 278350.

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 31440781 is about 5607.2079504866. The cubic root of 31440781 is about 315.6199464733.

The spelling of 31440781 in words is "thirty-one million, four hundred forty thousand, seven hundred eighty-one".