1620220981 has 6 divisors (see below), whose sum is σ = 1678018082. Its totient is φ = 1564350480.

The previous prime is 1620220967. The next prime is 1620220997. The reversal of 1620220981 is 1890220261.

It can be written as a sum of positive squares in 3 ways, for example, as 208340356 + 1411880625 = 14434^2 + 37575^2 .

It is not a de Polignac number, because 1620220981 - 2¹¹ = 1620218933 is a prime.

It is a super-2 number, since 2×1620220981² = 5250232054545204722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1620220961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 962430 + ... + 964111.

Almost surely, 2^1620220981 is an apocalyptic number.

It is an amenable number.

1620220981 is a deficient number, since it is larger than the sum of its proper divisors (57797101).

1620220981 is an equidigital number, since it uses as much as digits as its factorization.

1620220981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1926599 (or 1926570 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 1620220981 is about 40251.9686599302. The cubic root of 1620220981 is about 1174.5136918589.

The spelling of 1620220981 in words is "one billion, six hundred twenty million, two hundred twenty thousand, nine hundred eighty-one".