209491901 has 8 divisors (see below), whose sum is σ = 222739704. Its totient is φ = 196346880.

The previous prime is 209491897. The next prime is 209491907. The reversal of 209491901 is 109194902.

It can be written as a sum of positive squares in 4 ways, for example, as 123187801 + 86304100 = 11099^2 + 9290^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 209491901 - 2² = 209491897 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 (209491907) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21470 + ... + 29663.

It is an arithmetic number, because the mean of its divisors is an integer number (27842463).

Almost surely, 2^209491901 is an apocalyptic number.

It is an amenable number.

209491901 is a deficient number, since it is larger than the sum of its proper divisors (13247803).

209491901 is a wasteful number, since it uses less digits than its factorization.

209491901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51391.

The product of its (nonzero) digits is 5832, while the sum is 35.

The square root of 209491901 is about 14473.8350481135. The cubic root of 209491901 is about 593.9124270525.

The spelling of 209491901 in words is "two hundred nine million, four hundred ninety-one thousand, nine hundred one".