1620841581 has 24 divisors (see below), whose sum is σ = 2425789080. Its totient is φ = 1041645696.

The previous prime is 1620841571. The next prime is 1620841589. The reversal of 1620841581 is 1851480261.

1620841581 is a `hidden beast` number, since 16 + 20 + 8 + 41 + 581 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 303804900 + 1317036681 = 17430^2 + 36291^2 .

It is not a de Polignac number, because 1620841581 - 2⁵ = 1620841549 is a prime.

It is a super-2 number, since 2×1620841581² = 5254254861397159122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1620841589) 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 23 ways as a sum of consecutive naturals, for example, 172111 + ... + 181283.

It is an arithmetic number, because the mean of its divisors is an integer number (101074545).

Almost surely, 2^1620841581 is an apocalyptic number.

It is an amenable number.

1620841581 is a deficient number, since it is larger than the sum of its proper divisors (804947499).

1620841581 is a wasteful number, since it uses less digits than its factorization.

1620841581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9885 (or 9882 counting only the distinct ones).

The product of its (nonzero) digits is 15360, while the sum is 36.

The square root of 1620841581 is about 40259.6768615944. The cubic root of 1620841581 is about 1174.6636323424.

The spelling of 1620841581 in words is "one billion, six hundred twenty million, eight hundred forty-one thousand, five hundred eighty-one".