1981814720400 has 600 divisors, whose sum is σ = 7324003436904. Its totient is φ = 512909107200.

The previous prime is 1981814720377. The next prime is 1981814720467. The reversal of 1981814720400 is 40274181891.

1981814720400 is a `hidden beast` number, since 1 + 9 + 8 + 181 + 47 + 20 + 400 = 666.

It can be written as a sum of positive squares in 12 ways, for example, as 31066177536 + 1950748542864 = 176256^2 + 1396692^2 .

It is a tau number, because it is divible by the number of its divisors (600).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 261691014 + ... + 261698586.

Almost surely, 2^{1981814720400} is an apocalyptic number.

1981814720400 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 1981814720400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3662001718452).

1981814720400 is an abundant number, since it is smaller than the sum of its proper divisors (5342188716504).

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

1981814720400 is a wasteful number, since it uses less digits than its factorization.

1981814720400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7841 (or 7821 counting only the distinct ones).

The product of its (nonzero) digits is 129024, while the sum is 45.

The spelling of 1981814720400 in words is "one trillion, nine hundred eighty-one billion, eight hundred fourteen million, seven hundred twenty thousand, four hundred".