1563661 has 4 divisors (see below), whose sum is σ = 1705824. Its totient is φ = 1421500.

The previous prime is 1563649. The next prime is 1563689. The reversal of 1563661 is 1663651.

It is the 511-st star number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1663651 = 11 ⋅151241.

It is a cyclic number.

It is not a de Polignac number, because 1563661 - 2⁵ = 1563629 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 (1563631) 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, 71065 + ... + 71086.

It is an arithmetic number, because the mean of its divisors is an integer number (426456).

2^1563661 is an apocalyptic number.

1563661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1563661 is a deficient number, since it is larger than the sum of its proper divisors (142163).

1563661 is a wasteful number, since it uses less digits than its factorization.

1563661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142162.

The product of its digits is 3240, while the sum is 28.

The square root of 1563661 is about 1250.4643137651. The cubic root of 1563661 is about 116.0684544428.

The spelling of 1563661 in words is "one million, five hundred sixty-three thousand, six hundred sixty-one".