21210618 has 64 divisors (see below), whose sum is σ = 50803200. Its totient is φ = 5818560.

The previous prime is 21210587. The next prime is 21210619. The reversal of 21210618 is 81601212.

It is a junction number, because it is equal to n+sod(n) for n = 21210594 and 21210603.

It is not an unprimeable number, because it can be changed into a prime (21210619) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 50413 + ... + 50831.

It is an arithmetic number, because the mean of its divisors is an integer number (793800).

Almost surely, 2^21210618 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21210618, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25401600).

21210618 is an abundant number, since it is smaller than the sum of its proper divisors (29592582).

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

21210618 is a wasteful number, since it uses less digits than its factorization.

21210618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 507.

The product of its (nonzero) digits is 192, while the sum is 21.

The square root of 21210618 is about 4605.4986700682. The cubic root of 21210618 is about 276.8116989303.

The spelling of 21210618 in words is "twenty-one million, two hundred ten thousand, six hundred eighteen".