1561638 has 16 divisors (see below), whose sum is σ = 3363696. Its totient is φ = 480480.

The previous prime is 1561633. The next prime is 1561639. The reversal of 1561638 is 8361651.

It is a nialpdrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561633) 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 7 ways as a sum of consecutive naturals, for example, 9933 + ... + 10088.

It is an arithmetic number, because the mean of its divisors is an integer number (210231).

2^1561638 is an apocalyptic number.

1561638 is an abundant number, since it is smaller than the sum of its proper divisors (1802058).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1561638 is a wasteful number, since it uses less digits than its factorization.

1561638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20039.

The product of its digits is 4320, while the sum is 30.

The square root of 1561638 is about 1249.6551524321. The cubic root of 1561638 is about 116.0183779840.

The spelling of 1561638 in words is "one million, five hundred sixty-one thousand, six hundred thirty-eight".