21212620 has 48 divisors (see below), whose sum is σ = 52341408. Its totient is φ = 7119360.

The previous prime is 21212603. The next prime is 21212623. The reversal of 21212620 is 2621212.

It is a junction number, because it is equal to n+sod(n) for n = 21212594 and 21212603.

It is not an unprimeable number, because it can be changed into a prime (21212623) 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 15 ways as a sum of consecutive naturals, for example, 849 + ... + 6568.

It is an arithmetic number, because the mean of its divisors is an integer number (1090446).

Almost surely, 2^21212620 is an apocalyptic number.

21212620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21212620 is an abundant number, since it is smaller than the sum of its proper divisors (31128788).

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

21212620 is a wasteful number, since it uses less digits than its factorization.

21212620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7450 (or 7448 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 21212620 is about 4605.7160138246. The cubic root of 21212620 is about 276.8204077695.

Adding to 21212620 its reverse (2621212), we get a palindrome (23833832).

The spelling of 21212620 in words is "twenty-one million, two hundred twelve thousand, six hundred twenty".