2778661 has 4 divisors (see below), whose sum is σ = 2795872. Its totient is φ = 2761452.

The previous prime is 2778649. The next prime is 2778673. The reversal of 2778661 is 1668772.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (2778649) and next prime (2778673).

It is a cyclic number.

It is not a de Polignac number, because 2778661 - 2⁷ = 2778533 is a prime.

It is a Duffinian number.

2778661 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 2778661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2758661) 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, 8361 + ... + 8686.

It is an arithmetic number, because the mean of its divisors is an integer number (698968).

2^2778661 is an apocalyptic number.

It is an amenable number.

2778661 is a deficient number, since it is larger than the sum of its proper divisors (17211).

2778661 is a wasteful number, since it uses less digits than its factorization.

2778661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17210.

The product of its digits is 28224, while the sum is 37.

The square root of 2778661 is about 1666.9316122745. The cubic root of 2778661 is about 140.5870080743.

The spelling of 2778661 in words is "two million, seven hundred seventy-eight thousand, six hundred sixty-one".