6440278121 has 4 divisors (see below), whose sum is σ = 6441029700. Its totient is φ = 6439526544.

The previous prime is 6440278049. The next prime is 6440278129. The reversal of 6440278121 is 1218720446.

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 2223594025 + 4216684096 = 47155^2 + 64936^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6440278121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6440278129) 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, 362786 + ... + 380123.

It is an arithmetic number, because the mean of its divisors is an integer number (1610257425).

Almost surely, 2^6440278121 is an apocalyptic number.

It is an amenable number.

6440278121 is a deficient number, since it is larger than the sum of its proper divisors (751579).

6440278121 is an equidigital number, since it uses as much as digits as its factorization.

6440278121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 751578.

The product of its (nonzero) digits is 21504, while the sum is 35.

The square root of 6440278121 is about 80251.3434217771. The cubic root of 6440278121 is about 1860.5222760616.

Adding to 6440278121 its reverse (1218720446), we get a palindrome (7658998567).

The spelling of 6440278121 in words is "six billion, four hundred forty million, two hundred seventy-eight thousand, one hundred twenty-one".