217421901 has 20 divisors (see below), whose sum is σ = 329646592. Its totient is φ = 142780968.

The previous prime is 217421899. The next prime is 217421909. The reversal of 217421901 is 109124712.

It is not a de Polignac number, because 217421901 - 2¹ = 217421899 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217421909) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 14605 + ... + 25458.

Almost surely, 2^217421901 is an apocalyptic number.

It is an amenable number.

217421901 is a deficient number, since it is larger than the sum of its proper divisors (112224691).

217421901 is an equidigital number, since it uses as much as digits as its factorization.

217421901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40142 (or 40133 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 217421901 is about 14745.2331619408. The cubic root of 217421901 is about 601.3136965696.

The spelling of 217421901 in words is "two hundred seventeen million, four hundred twenty-one thousand, nine hundred one".