209091025 has 54 divisors (see below), whose sum is σ = 309348690. Its totient is φ = 140025600.

The previous prime is 209090977. The next prime is 209091031. The reversal of 209091025 is 520190902.

209091025 is a nontrivial binomial coefficient, being equal to C(20450, 2).

It can be written as a sum of positive squares in 9 ways, for example, as 82955664 + 126135361 = 9108^2 + 11231^2 .

It is not a de Polignac number, because 209091025 - 2¹³ = 209082833 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 209090984 and 209091002.

It is an unprimeable number.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 511021 + ... + 511429.

Almost surely, 2^209091025 is an apocalyptic number.

209091025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

209091025 is the 20449-th triangular number and also the 10225-th hexagonal number.

209091025 is the 6817-th centered nonagonal number.

It is an amenable number.

209091025 is a deficient number, since it is larger than the sum of its proper divisors (100257665).

209091025 is a wasteful number, since it uses less digits than its factorization.

209091025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 467 (or 438 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 28.

The square root of 209091025 is about 14459.9801175520. The cubic root of 209091025 is about 593.5333554952.

The spelling of 209091025 in words is "two hundred nine million, ninety-one thousand, twenty-five".