1981504640 has 64 divisors (see below), whose sum is σ = 4826495160. Its totient is φ = 777633792.

The previous prime is 1981504639. The next prime is 1981504643. The reversal of 1981504640 is 464051891.

It can be written as a sum of positive squares in 4 ways, for example, as 1959301696 + 22202944 = 44264^2 + 4712^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is a junction number, because it is equal to n+sod(n) for n = 1981504594 and 1981504603.

It is not an unprimeable number, because it can be changed into a prime (1981504643) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4712 + ... + 63128.

Almost surely, 2^1981504640 is an apocalyptic number.

1981504640 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 1981504640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2413247580).

1981504640 is an abundant number, since it is smaller than the sum of its proper divisors (2844990520).

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

1981504640 is an equidigital number, since it uses as much as digits as its factorization.

1981504640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58489 (or 58477 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 38.

The square root of 1981504640 is about 44514.0948464641. The cubic root of 1981504640 is about 1256.0252337825.

The spelling of 1981504640 in words is "one billion, nine hundred eighty-one million, five hundred four thousand, six hundred forty".