172209561 has 8 divisors (see below), whose sum is σ = 233945280. Its totient is φ = 112640112.

The previous prime is 172209517. The next prime is 172209589. The reversal of 172209561 is 165902271.

172209561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 172209561 - 2¹⁰ = 172208537 is a prime.

It is a super-2 number, since 2×172209561² = 59312265799625442, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (172209761) 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, 541381 + ... + 541698.

It is an arithmetic number, because the mean of its divisors is an integer number (29243160).

Almost surely, 2^172209561 is an apocalyptic number.

It is an amenable number.

172209561 is a deficient number, since it is larger than the sum of its proper divisors (61735719).

172209561 is a wasteful number, since it uses less digits than its factorization.

172209561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1083135.

The product of its (nonzero) digits is 7560, while the sum is 33.

The square root of 172209561 is about 13122.8640547710. The cubic root of 172209561 is about 556.3555437315.

The spelling of 172209561 in words is "one hundred seventy-two million, two hundred nine thousand, five hundred sixty-one".