21255018 has 8 divisors (see below), whose sum is σ = 42510048. Its totient is φ = 7085004.

The previous prime is 21254993. The next prime is 21255019. The reversal of 21255018 is 81055212.

It is a sphenic number, since it is the product of 3 distinct primes.

21255018 is an admirable number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21255019) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1771246 + ... + 1771257.

It is an arithmetic number, because the mean of its divisors is an integer number (5313756).

Almost surely, 2^21255018 is an apocalyptic number.

21255018 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21255018 is a wasteful number, since it uses less digits than its factorization.

21255018 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3542508.

The product of its (nonzero) digits is 800, while the sum is 24.

The square root of 21255018 is about 4610.3164750373. The cubic root of 21255018 is about 277.0047134788.

The spelling of 21255018 in words is "twenty-one million, two hundred fifty-five thousand, eighteen".