40042781 has 4 divisors (see below), whose sum is σ = 40185564. Its totient is φ = 39900000.

The previous prime is 40042757. The next prime is 40042789. The reversal of 40042781 is 18724004.

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 20160100 + 19882681 = 4490^2 + 4459^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-40042781 is a prime.

It is a super-2 number, since 2×40042781² = 3206848620427922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 40042781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (40042789) 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, 70970 + ... + 71531.

It is an arithmetic number, because the mean of its divisors is an integer number (10046391).

Almost surely, 2^40042781 is an apocalyptic number.

It is an amenable number.

40042781 is a deficient number, since it is larger than the sum of its proper divisors (142783).

40042781 is a wasteful number, since it uses less digits than its factorization.

40042781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142782.

The product of its (nonzero) digits is 1792, while the sum is 26.

The square root of 40042781 is about 6327.9365515150. The cubic root of 40042781 is about 342.1170700291.

Adding to 40042781 its reverse (18724004), we get a palindrome (58766785).

The spelling of 40042781 in words is "forty million, forty-two thousand, seven hundred eighty-one".