1561121560 has 128 divisors (see below), whose sum is σ = 3881779200. Its totient is φ = 562452480.

The previous prime is 1561121557. The next prime is 1561121563. The reversal of 1561121560 is 651211651.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1561121557) and next prime (1561121563).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561121563) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2170881 + ... + 2171599.

It is an arithmetic number, because the mean of its divisors is an integer number (30326400).

Almost surely, 2^1561121560 is an apocalyptic number.

1561121560 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1561121560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1940889600).

1561121560 is an abundant number, since it is smaller than the sum of its proper divisors (2320657640).

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

1561121560 is a wasteful number, since it uses less digits than its factorization.

1561121560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 881 (or 877 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 28.

The square root of 1561121560 is about 39511.0308648104. The cubic root of 1561121560 is about 1160.0558732501.

Subtracting from 1561121560 its reverse (651211651), we obtain a palindrome (909909909).

The spelling of 1561121560 in words is "one billion, five hundred sixty-one million, one hundred twenty-one thousand, five hundred sixty".