2780639 has 4 divisors (see below), whose sum is σ = 2944224. Its totient is φ = 2617056.

The previous prime is 2780623. The next prime is 2780641. The reversal of 2780639 is 9360872.

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

It is a cyclic number.

It is not a de Polignac number, because 2780639 - 2⁴ = 2780623 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2780599 and 2780608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2780039) 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, 81767 + ... + 81800.

It is an arithmetic number, because the mean of its divisors is an integer number (736056).

2^2780639 is an apocalyptic number.

2780639 is a deficient number, since it is larger than the sum of its proper divisors (163585).

2780639 is a wasteful number, since it uses less digits than its factorization.

2780639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163584.

The product of its (nonzero) digits is 18144, while the sum is 35.

The square root of 2780639 is about 1667.5248124091. The cubic root of 2780639 is about 140.6203592872.

The spelling of 2780639 in words is "two million, seven hundred eighty thousand, six hundred thirty-nine".