1561664020 has 96 divisors (see below), whose sum is σ = 3812417280. Its totient is φ = 526310400.

The previous prime is 1561664011. The next prime is 1561664053. The reversal of 1561664020 is 204661651.

It is a super-2 number, since 2×1561664020² = 4877589022725120800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2530752 + ... + 2531368.

It is an arithmetic number, because the mean of its divisors is an integer number (39712680).

Almost surely, 2^1561664020 is an apocalyptic number.

1561664020 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 1561664020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1906208640).

1561664020 is an abundant number, since it is smaller than the sum of its proper divisors (2250753260).

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

1561664020 is a wasteful number, since it uses less digits than its factorization.

1561664020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 913 (or 911 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 1561664020 is about 39517.8949338145. The cubic root of 1561664020 is about 1160.1902234615.

The spelling of 1561664020 in words is "one billion, five hundred sixty-one million, six hundred sixty-four thousand, twenty".