1561618 has 4 divisors (see below), whose sum is σ = 2342430. Its totient is φ = 780808.

The previous prime is 1561607. The next prime is 1561633. The reversal of 1561618 is 8161651.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 8161651 = 113 ⋅72227.

It can be written as a sum of positive squares in only one way, i.e., 1129969 + 431649 = 1063^2 + 657^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390403 + ... + 390406.

2^1561618 is an apocalyptic number.

1561618 is a deficient number, since it is larger than the sum of its proper divisors (780812).

1561618 is an equidigital number, since it uses as much as digits as its factorization.

1561618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 780811.

The product of its digits is 1440, while the sum is 28.

The square root of 1561618 is about 1249.6471501988. The cubic root of 1561618 is about 116.0178826969.

The spelling of 1561618 in words is "one million, five hundred sixty-one thousand, six hundred eighteen".