209131397 has 4 divisors (see below), whose sum is σ = 209161836. Its totient is φ = 209100960.

The previous prime is 209131381. The next prime is 209131409. The reversal of 209131397 is 793131902.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 178649956 + 30481441 = 13366^2 + 5521^2 .

It is a cyclic number.

It is not a de Polignac number, because 209131397 - 2⁴ = 209131381 is a prime.

It is a super-2 number, since 2×209131397² = 87471882422343218, 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 (209131337) 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, 497 + ... + 20457.

It is an arithmetic number, because the mean of its divisors is an integer number (52290459).

Almost surely, 2^209131397 is an apocalyptic number.

It is an amenable number.

209131397 is a deficient number, since it is larger than the sum of its proper divisors (30439).

209131397 is a wasteful number, since it uses less digits than its factorization.

209131397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30438.

The product of its (nonzero) digits is 10206, while the sum is 35.

The square root of 209131397 is about 14461.3760410274. The cubic root of 209131397 is about 593.5715535105.

The spelling of 209131397 in words is "two hundred nine million, one hundred thirty-one thousand, three hundred ninety-seven".