6442781 has 4 divisors (see below), whose sum is σ = 6599964. Its totient is φ = 6285600.

The previous prime is 6442771. The next prime is 6442801. The reversal of 6442781 is 1872446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1872446 = 2 ⋅936223.

It can be written as a sum of positive squares in 2 ways, for example, as 2775556 + 3667225 = 1666^2 + 1915^2 .

It is a cyclic number.

It is not a de Polignac number, because 6442781 - 2¹⁴ = 6426397 is a prime.

It is a super-2 number, since 2×6442781² = 83018854027922, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6442721) 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, 78530 + ... + 78611.

It is an arithmetic number, because the mean of its divisors is an integer number (1649991).

Almost surely, 2^6442781 is an apocalyptic number.

It is an amenable number.

6442781 is a deficient number, since it is larger than the sum of its proper divisors (157183).

6442781 is a wasteful number, since it uses less digits than its factorization.

6442781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157182.

The product of its digits is 10752, while the sum is 32.

The square root of 6442781 is about 2538.2633827087. The cubic root of 6442781 is about 186.0763262498.

The spelling of 6442781 in words is "six million, four hundred forty-two thousand, seven hundred eighty-one".