218687421 has 4 divisors (see below), whose sum is σ = 291583232. Its totient is φ = 145791612.

The previous prime is 218687389. The next prime is 218687429. The reversal of 218687421 is 124786812.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 218687421 - 2⁵ = 218687389 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 218687421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218687429) 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, 36447901 + ... + 36447906.

It is an arithmetic number, because the mean of its divisors is an integer number (72895808).

Almost surely, 2^218687421 is an apocalyptic number.

It is an amenable number.

218687421 is a deficient number, since it is larger than the sum of its proper divisors (72895811).

218687421 is an equidigital number, since it uses as much as digits as its factorization.

218687421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72895810.

The product of its digits is 43008, while the sum is 39.

The square root of 218687421 is about 14788.0837501010. The cubic root of 218687421 is about 602.4781036905.

The spelling of 218687421 in words is "two hundred eighteen million, six hundred eighty-seven thousand, four hundred twenty-one".