1561633920 has 576 divisors, whose sum is σ = 6856799040. Its totient is φ = 323850240.

The previous prime is 1561633907. The next prime is 1561633939. The reversal of 1561633920 is 293361651.

1561633920 is a `hidden beast` number, since 1 + 5 + 616 + 3 + 39 + 2 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (576).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

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 71 ways as a sum of consecutive naturals, for example, 3104389 + ... + 3104891.

It is an arithmetic number, because the mean of its divisors is an integer number (11904165).

Almost surely, 2^1561633920 is an apocalyptic number.

1561633920 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 1561633920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3428399520).

1561633920 is an abundant number, since it is smaller than the sum of its proper divisors (5295165120).

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

1561633920 is a wasteful number, since it uses less digits than its factorization.

1561633920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553 (or 531 counting only the distinct ones).

The product of its (nonzero) digits is 29160, while the sum is 36.

The square root of 1561633920 is about 39517.5140918555. The cubic root of 1561633920 is about 1160.1827694574.

The spelling of 1561633920 in words is "one billion, five hundred sixty-one million, six hundred thirty-three thousand, nine hundred twenty".