1641646981 has 4 divisors (see below), whose sum is σ = 1767927532. Its totient is φ = 1515366432.

The previous prime is 1641646967. The next prime is 1641647003. The reversal of 1641646981 is 1896461461.

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 1076824225 + 564822756 = 32815^2 + 23766^2 .

It is a cyclic number.

It is not a de Polignac number, because 1641646981 - 2²⁹ = 1104776069 is a prime.

It is a super-2 number, since 2×1641646981² = 5390009620452828722, 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 (1641646921) 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, 63140256 + ... + 63140281.

It is an arithmetic number, because the mean of its divisors is an integer number (441981883).

Almost surely, 2^1641646981 is an apocalyptic number.

It is an amenable number.

1641646981 is a deficient number, since it is larger than the sum of its proper divisors (126280551).

1641646981 is a wasteful number, since it uses less digits than its factorization.

1641646981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126280550.

The product of its digits is 248832, while the sum is 46.

The square root of 1641646981 is about 40517.2430083785. The cubic root of 1641646981 is about 1179.6683404298.

The spelling of 1641646981 in words is "one billion, six hundred forty-one million, six hundred forty-six thousand, nine hundred eighty-one".