218931021 has 24 divisors (see below), whose sum is σ = 334414080. Its totient is φ = 137793600.

The previous prime is 218931007. The next prime is 218931047. The reversal of 218931021 is 120139812.

It is not a de Polignac number, because 218931021 - 2⁵ = 218930989 is a prime.

It is a super-2 number, since 2×218931021² = 95861583912204882, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218931071) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1870 + ... + 21008.

It is an arithmetic number, because the mean of its divisors is an integer number (13933920).

Almost surely, 2^218931021 is an apocalyptic number.

It is an amenable number.

218931021 is a deficient number, since it is larger than the sum of its proper divisors (115483059).

218931021 is a wasteful number, since it uses less digits than its factorization.

218931021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19217 (or 19214 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 218931021 is about 14796.3178189710. The cubic root of 218931021 is about 602.7017245475.

The spelling of 218931021 in words is "two hundred eighteen million, nine hundred thirty-one thousand, twenty-one".