201640661 has 4 divisors (see below), whose sum is σ = 201681900. Its totient is φ = 201599424.

The previous prime is 201640651. The next prime is 201640679. The reversal of 201640661 is 166046102.

It is a happy number.

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 135722500 + 65918161 = 11650^2 + 8119^2 .

It is a cyclic number.

It is not a de Polignac number, because 201640661 - 2²² = 197446357 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 201640661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (201640601) 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, 12116 + ... + 23453.

It is an arithmetic number, because the mean of its divisors is an integer number (50420475).

Almost surely, 2^201640661 is an apocalyptic number.

It is an amenable number.

201640661 is a deficient number, since it is larger than the sum of its proper divisors (41239).

201640661 is an equidigital number, since it uses as much as digits as its factorization.

201640661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41238.

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 201640661 is about 14200.0232746288. The cubic root of 201640661 is about 586.3983020960.

Adding to 201640661 its reverse (166046102), we get a palindrome (367686763).

The spelling of 201640661 in words is "two hundred one million, six hundred forty thousand, six hundred sixty-one".