1661287 has 6 divisors (see below), whose sum is σ = 1690728. Its totient is φ = 1632204.

The previous prime is 1661281. The next prime is 1661293. The reversal of 1661287 is 7821661.

It is an interprime number because it is at equal distance from previous prime (1661281) and next prime (1661293).

It is not a de Polignac number, because 1661287 - 2⁷ = 1661159 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661281) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 13018 + ... + 13144.

It is an arithmetic number, because the mean of its divisors is an integer number (281788).

2^1661287 is an apocalyptic number.

1661287 is a deficient number, since it is larger than the sum of its proper divisors (29441).

1661287 is an equidigital number, since it uses as much as digits as its factorization.

1661287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 357 (or 230 counting only the distinct ones).

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

The square root of 1661287 is about 1288.9092287667. The cubic root of 1661287 is about 118.4354066482.

The spelling of 1661287 in words is "one million, six hundred sixty-one thousand, two hundred eighty-seven".