1981020065 has 4 divisors (see below), whose sum is σ = 2377224084. Its totient is φ = 1584816048.

The previous prime is 1981020031. The next prime is 1981020109. The reversal of 1981020065 is 5600201891.

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 1368408064 + 612612001 = 36992^2 + 24751^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981020065 - 2¹⁴ = 1981003681 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 198102002 + ... + 198102011.

It is an arithmetic number, because the mean of its divisors is an integer number (594306021).

Almost surely, 2^1981020065 is an apocalyptic number.

It is an amenable number.

1981020065 is a deficient number, since it is larger than the sum of its proper divisors (396204019).

1981020065 is an equidigital number, since it uses as much as digits as its factorization.

1981020065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 396204018.

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 1981020065 is about 44508.6515747220. The cubic root of 1981020065 is about 1255.9228388589.

The spelling of 1981020065 in words is "one billion, nine hundred eighty-one million, twenty thousand, sixty-five".