213864021 has 24 divisors (see below), whose sum is σ = 355430400. Its totient is φ = 121382496.

The previous prime is 213864017. The next prime is 213864023. The reversal of 213864021 is 120468312.

213864021 is a `hidden beast` number, since 2 + 13 + 8 + 640 + 2 + 1 = 666.

It is not a de Polignac number, because 213864021 - 2² = 213864017 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (213864023) 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 23 ways as a sum of consecutive naturals, for example, 2005 + ... + 20778.

It is an arithmetic number, because the mean of its divisors is an integer number (14809600).

Almost surely, 2^213864021 is an apocalyptic number.

213864021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

213864021 is a deficient number, since it is larger than the sum of its proper divisors (141566379).

213864021 is a wasteful number, since it uses less digits than its factorization.

213864021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22945 (or 22942 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 213864021 is about 14624.0904332543. The cubic root of 213864021 is about 598.0156864004.

The spelling of 213864021 in words is "two hundred thirteen million, eight hundred sixty-four thousand, twenty-one".