1551665 has 4 divisors (see below), whose sum is σ = 1862004. Its totient is φ = 1241328.

The previous prime is 1551661. The next prime is 1551677. The reversal of 1551665 is 5661551.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5661551 = 7 ⋅808793.

It can be written as a sum of positive squares in 2 ways, for example, as 817216 + 734449 = 904^2 + 857^2 .

It is a cyclic number.

It is not a de Polignac number, because 1551665 - 2² = 1551661 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1551661) 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, 155162 + ... + 155171.

It is an arithmetic number, because the mean of its divisors is an integer number (465501).

2^1551665 is an apocalyptic number.

It is an amenable number.

1551665 is a deficient number, since it is larger than the sum of its proper divisors (310339).

1551665 is an equidigital number, since it uses as much as digits as its factorization.

1551665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 310338.

The product of its digits is 4500, while the sum is 29.

The square root of 1551665 is about 1245.6584604136. The cubic root of 1551665 is about 115.7708765079.

The spelling of 1551665 in words is "one million, five hundred fifty-one thousand, six hundred sixty-five".