21213018 has 24 divisors (see below), whose sum is σ = 47032128. Its totient is φ = 6906312.

The previous prime is 21213013. The next prime is 21213029. The reversal of 21213018 is 81031212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21213011) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12930 + ... + 14477.

It is an arithmetic number, because the mean of its divisors is an integer number (1959672).

Almost surely, 2^21213018 is an apocalyptic number.

21213018 is an abundant number, since it is smaller than the sum of its proper divisors (25819110).

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

21213018 is a wasteful number, since it uses less digits than its factorization.

21213018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27458 (or 27455 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 21213018 is about 4605.7592208017. The cubic root of 21213018 is about 276.8221390319.

The spelling of 21213018 in words is "twenty-one million, two hundred thirteen thousand, eighteen".