42409781 has 4 divisors (see below), whose sum is σ = 44904492. Its totient is φ = 39915072.

The previous prime is 42409777. The next prime is 42409793. The reversal of 42409781 is 18790424.

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 36844900 + 5564881 = 6070^2 + 2359^2 .

It is a cyclic number.

It is not a de Polignac number, because 42409781 - 2² = 42409777 is a prime.

It is a super-3 number, since 3×42409781³ (a number of 24 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (42409751) 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, 1247330 + ... + 1247363.

It is an arithmetic number, because the mean of its divisors is an integer number (11226123).

Almost surely, 2^42409781 is an apocalyptic number.

It is an amenable number.

42409781 is a deficient number, since it is larger than the sum of its proper divisors (2494711).

42409781 is a wasteful number, since it uses less digits than its factorization.

42409781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2494710.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 42409781 is about 6512.2792476982. The cubic root of 42409781 is about 348.7294915635.

The spelling of 42409781 in words is "forty-two million, four hundred nine thousand, seven hundred eighty-one".