1561655 has 4 divisors (see below), whose sum is σ = 1873992. Its totient is φ = 1249320.

The previous prime is 1561639. The next prime is 1561657. The reversal of 1561655 is 5561651.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 1561655 - 2⁴ = 1561639 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 (1561657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 156161 + ... + 156170.

It is an arithmetic number, because the mean of its divisors is an integer number (468498).

2^1561655 is an apocalyptic number.

1561655 is a deficient number, since it is larger than the sum of its proper divisors (312337).

1561655 is an equidigital number, since it uses as much as digits as its factorization.

1561655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312336.

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

The square root of 1561655 is about 1249.6619542900. The cubic root of 1561655 is about 116.0187989747.

The spelling of 1561655 in words is "one million, five hundred sixty-one thousand, six hundred fifty-five".