1561091100 has 36 divisors (see below), whose sum is σ = 4516757784. Its totient is φ = 416290880.

The previous prime is 1561091099. The next prime is 1561091101. The reversal of 1561091100 is 11901651.

It is an interprime number because it is at equal distance from previous prime (1561091099) and next prime (1561091101).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561091101) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2601519 + ... + 2602118.

It is an arithmetic number, because the mean of its divisors is an integer number (125465494).

Almost surely, 2^1561091100 is an apocalyptic number.

1561091100 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1561091100 is an abundant number, since it is smaller than the sum of its proper divisors (2955666684).

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

1561091100 is a wasteful number, since it uses less digits than its factorization.

1561091100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5203654 (or 5203647 counting only the distinct ones).

The product of its (nonzero) digits is 270, while the sum is 24.

The square root of 1561091100 is about 39510.6454009549. The cubic root of 1561091100 is about 1160.0483283472.

Adding to 1561091100 its reverse (11901651), we get a palindrome (1572992751).

The spelling of 1561091100 in words is "one billion, five hundred sixty-one million, ninety-one thousand, one hundred".