1981615345 has 4 divisors (see below), whose sum is σ = 2377938420. Its totient is φ = 1585292272.

The previous prime is 1981615343. The next prime is 1981615373. The reversal of 1981615345 is 5435161891.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 862244496 + 1119370849 = 29364^2 + 33457^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981615345 - 2¹ = 1981615343 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1981615343) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 198161530 + ... + 198161539.

It is an arithmetic number, because the mean of its divisors is an integer number (594484605).

Almost surely, 2^1981615345 is an apocalyptic number.

It is an amenable number.

1981615345 is a deficient number, since it is larger than the sum of its proper divisors (396323075).

1981615345 is an equidigital number, since it uses as much as digits as its factorization.

1981615345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 396323074.

The product of its digits is 129600, while the sum is 43.

The square root of 1981615345 is about 44515.3383116427. The cubic root of 1981615345 is about 1256.0486243718.

The spelling of 1981615345 in words is "one billion, nine hundred eighty-one million, six hundred fifteen thousand, three hundred forty-five".