1561217660 has 24 divisors (see below), whose sum is σ = 3384318336. Its totient is φ = 604342080.

The previous prime is 1561217611. The next prime is 1561217663. The reversal of 1561217660 is 667121651.

It is a self number, because there is not a number n which added to its sum of digits gives 1561217660.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561217663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1258427 + ... + 1259666.

It is an arithmetic number, because the mean of its divisors is an integer number (141013264).

Almost surely, 2^1561217660 is an apocalyptic number.

1561217660 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1561217660 is an abundant number, since it is smaller than the sum of its proper divisors (1823100676).

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

1561217660 is a wasteful number, since it uses less digits than its factorization.

1561217660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2518133 (or 2518131 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 1561217660 is about 39512.2469621762. The cubic root of 1561217660 is about 1160.0796764534.

The spelling of 1561217660 in words is "one billion, five hundred sixty-one million, two hundred seventeen thousand, six hundred sixty".