1561121616 has 20 divisors (see below), whose sum is σ = 4032897632. Its totient is φ = 520373856.

The previous prime is 1561121599. The next prime is 1561121623. The reversal of 1561121616 is 6161211651.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16261636 + ... + 16261731.

Almost surely, 2^1561121616 is an apocalyptic number.

1561121616 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

1561121616 is an abundant number, since it is smaller than the sum of its proper divisors (2471776016).

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

1561121616 is a wasteful number, since it uses less digits than its factorization.

1561121616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32523378 (or 32523372 counting only the distinct ones).

The product of its digits is 2160, while the sum is 30.

The square root of 1561121616 is about 39511.0315734732. The cubic root of 1561121616 is about 1160.0558871211.

The spelling of 1561121616 in words is "one billion, five hundred sixty-one million, one hundred twenty-one thousand, six hundred sixteen".