1551861 has 12 divisors (see below), whose sum is σ = 2253420. Its totient is φ = 1029120.

The previous prime is 1551859. The next prime is 1551871. The reversal of 1551861 is 1681551.

It can be written as a sum of positive squares in 2 ways, for example, as 731025 + 820836 = 855^2 + 906^2 .

It is not a de Polignac number, because 1551861 - 2¹ = 1551859 is a prime.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1551871) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2101 + ... + 2741.

It is an arithmetic number, because the mean of its divisors is an integer number (187785).

2^1551861 is an apocalyptic number.

It is an amenable number.

1551861 is a deficient number, since it is larger than the sum of its proper divisors (701559).

1551861 is a wasteful number, since it uses less digits than its factorization.

1551861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 916 (or 913 counting only the distinct ones).

The product of its digits is 1200, while the sum is 27.

The square root of 1551861 is about 1245.7371311798. The cubic root of 1551861 is about 115.7757508712.

It can be divided in two parts, 155 and 1861, that added together give a triangular number (2016 = T₆₃).

The spelling of 1551861 in words is "one million, five hundred fifty-one thousand, eight hundred sixty-one".