1981450626817 has 4 divisors (see below), whose sum is σ = 1981783481860. Its totient is φ = 1981117771776.

The previous prime is 1981450626809. The next prime is 1981450626853. The reversal of 1981450626817 is 7186260541891.

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 13726231281 + 1967724395536 = 117159^2 + 1402756^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981450626817 - 2³ = 1981450626809 is a prime.

It is a super-3 number, since 3×1981450626817³ (a number of 38 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1981450620817) 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, 166418592 + ... + 166430497.

It is an arithmetic number, because the mean of its divisors is an integer number (495445870465).

Almost surely, 2^{1981450626817} is an apocalyptic number.

It is an amenable number.

1981450626817 is a deficient number, since it is larger than the sum of its proper divisors (332855043).

1981450626817 is an equidigital number, since it uses as much as digits as its factorization.

1981450626817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 332855042.

The product of its (nonzero) digits is 5806080, while the sum is 58.

The spelling of 1981450626817 in words is "one trillion, nine hundred eighty-one billion, four hundred fifty million, six hundred twenty-six thousand, eight hundred seventeen".