209702421 has 12 divisors (see below), whose sum is σ = 311090572. Its totient is φ = 136022976.

The previous prime is 209702417. The next prime is 209702453. The reversal of 209702421 is 124207902.

It can be written as a sum of positive squares in 2 ways, for example, as 155900196 + 53802225 = 12486^2 + 7335^2 .

It is not a de Polignac number, because 209702421 - 2² = 209702417 is a prime.

It is a super-2 number, since 2×209702421² = 87950210746522482, 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 (209702621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 314536 + ... + 315201.

Almost surely, 2^209702421 is an apocalyptic number.

It is an amenable number.

209702421 is a deficient number, since it is larger than the sum of its proper divisors (101388151).

209702421 is a wasteful number, since it uses less digits than its factorization.

209702421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 629780 (or 629777 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 209702421 is about 14481.1056553013. The cubic root of 209702421 is about 594.1113028174. Note that the first 3 decimals are identical.

The spelling of 209702421 in words is "two hundred nine million, seven hundred two thousand, four hundred twenty-one".