201691391 has 6 divisors (see below), whose sum is σ = 221693976. Its totient is φ = 183355700.

The previous prime is 201691379. The next prime is 201691409. The reversal of 201691391 is 193196102.

201691391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 201691391 - 2¹⁸ = 201429247 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (201691331) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 833315 + ... + 833556.

It is an arithmetic number, because the mean of its divisors is an integer number (36948996).

Almost surely, 2^201691391 is an apocalyptic number.

201691391 is a deficient number, since it is larger than the sum of its proper divisors (20002585).

201691391 is a wasteful number, since it uses less digits than its factorization.

201691391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1666893 (or 1666882 counting only the distinct ones).

The product of its (nonzero) digits is 2916, while the sum is 32.

The square root of 201691391 is about 14201.8094269709. The cubic root of 201691391 is about 586.4474745386.

The spelling of 201691391 in words is "two hundred one million, six hundred ninety-one thousand, three hundred ninety-one".