1661491 has 4 divisors (see below), whose sum is σ = 1789312. Its totient is φ = 1533672.

The previous prime is 1661489. The next prime is 1661503. The reversal of 1661491 is 1941661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1941661 = 223 ⋅8707.

It is a cyclic number.

It is not a de Polignac number, because 1661491 - 2¹ = 1661489 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 (1661431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63891 + ... + 63916.

It is an arithmetic number, because the mean of its divisors is an integer number (447328).

2^1661491 is an apocalyptic number.

1661491 is a deficient number, since it is larger than the sum of its proper divisors (127821).

1661491 is a wasteful number, since it uses less digits than its factorization.

1661491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127820.

The product of its digits is 1296, while the sum is 28.

The square root of 1661491 is about 1288.9883630196. The cubic root of 1661491 is about 118.4402542621.

The spelling of 1661491 in words is "one million, six hundred sixty-one thousand, four hundred ninety-one".