21213040 has 20 divisors (see below), whose sum is σ = 49320504. Its totient is φ = 8485184.

The previous prime is 21213029. The next prime is 21213041. The reversal of 21213040 is 4031212.

It is a tau number, because it is divible by the number of its divisors (20).

It is a self number, because there is not a number n which added to its sum of digits gives 21213040.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 132502 + ... + 132661.

Almost surely, 2^21213040 is an apocalyptic number.

21213040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21213040 is an abundant number, since it is smaller than the sum of its proper divisors (28107464).

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

21213040 is a wasteful number, since it uses less digits than its factorization.

21213040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 265176 (or 265170 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21213040 is about 4605.7616091153. The cubic root of 21213040 is about 276.8222347292.

Adding to 21213040 its reverse (4031212), we get a palindrome (25244252).

The spelling of 21213040 in words is "twenty-one million, two hundred thirteen thousand, forty".