209821642 has 8 divisors (see below), whose sum is σ = 317848932. Its totient is φ = 103872000.

The previous prime is 209821631. The next prime is 209821643. The reversal of 209821642 is 246128902.

209821642 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 208542481 + 1279161 = 14441^2 + 1131^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 209821598 and 209821607.

It is not an unprimeable number, because it can be changed into a prime (209821643) 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, 519159 + ... + 519562.

Almost surely, 2^209821642 is an apocalyptic number.

209821642 is a deficient number, since it is larger than the sum of its proper divisors (108027290).

209821642 is a wasteful number, since it uses less digits than its factorization.

209821642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1038824.

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 209821642 is about 14485.2215033116. The cubic root of 209821642 is about 594.2238704653.

The spelling of 209821642 in words is "two hundred nine million, eight hundred twenty-one thousand, six hundred forty-two".