19561998720 has 768 divisors, whose sum is σ = 75922272000. Its totient is φ = 4231987200.

The previous prime is 19561998689. The next prime is 19561998737. The reversal of 19561998720 is 2789916591.

It is a Harshad number since it is a multiple of its sum of digits (57).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 477121900 + ... + 477121940.

It is an arithmetic number, because the mean of its divisors is an integer number (98857125).

Almost surely, 2^19561998720 is an apocalyptic number.

19561998720 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 19561998720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37961136000).

19561998720 is an abundant number, since it is smaller than the sum of its proper divisors (56360273280).

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

19561998720 is a wasteful number, since it uses less digits than its factorization.

19561998720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163 (or 110 counting only the distinct ones).

The product of its (nonzero) digits is 2449440, while the sum is 57.

The spelling of 19561998720 in words is "nineteen billion, five hundred sixty-one million, nine hundred ninety-eight thousand, seven hundred twenty".