201661921 has 4 divisors (see below), whose sum is σ = 201982144. Its totient is φ = 201341700.

The previous prime is 201661919. The next prime is 201661927. The reversal of 201661921 is 129166102.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 201661921 - 2¹ = 201661919 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 201661921.

It is not an unprimeable number, because it can be changed into a prime (201661927) 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, 159165 + ... + 160426.

It is an arithmetic number, because the mean of its divisors is an integer number (50495536).

Almost surely, 2^201661921 is an apocalyptic number.

It is an amenable number.

201661921 is a deficient number, since it is larger than the sum of its proper divisors (320223).

201661921 is an equidigital number, since it uses as much as digits as its factorization.

201661921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320222.

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 201661921 is about 14200.7718452202. The cubic root of 201661921 is about 586.4189103565.

The spelling of 201661921 in words is "two hundred one million, six hundred sixty-one thousand, nine hundred twenty-one".