2781661 has 8 divisors (see below), whose sum is σ = 2920448. Its totient is φ = 2646000.

The previous prime is 2781637. The next prime is 2781677. The reversal of 2781661 is 1661872.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 3-Lehmer number, since φ(2781661) divides (2781661-1)³.

It is a cyclic number.

It is not a de Polignac number, because 2781661 - 2⁵ = 2781629 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2781061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1156 + ... + 2626.

It is an arithmetic number, because the mean of its divisors is an integer number (365056).

2^2781661 is an apocalyptic number.

It is an amenable number.

2781661 is a deficient number, since it is larger than the sum of its proper divisors (138787).

2781661 is a wasteful number, since it uses less digits than its factorization.

2781661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1563.

The product of its digits is 4032, while the sum is 31.

The square root of 2781661 is about 1667.8312264735. The cubic root of 2781661 is about 140.6375851124.

The spelling of 2781661 in words is "two million, seven hundred eighty-one thousand, six hundred sixty-one".