21213400420 has 12 divisors (see below), whose sum is σ = 44548140924. Its totient is φ = 8485360160.

The previous prime is 21213400393. The next prime is 21213400441. The reversal of 21213400420 is 2400431212.

It can be written as a sum of positive squares in 2 ways, for example, as 7602444864 + 13610955556 = 87192^2 + 116666^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 530334991 + ... + 530335030.

It is an arithmetic number, because the mean of its divisors is an integer number (3712345077).

Almost surely, 2^21213400420 is an apocalyptic number.

21213400420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21213400420 is an abundant number, since it is smaller than the sum of its proper divisors (23334740504).

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

21213400420 is a wasteful number, since it uses less digits than its factorization.

21213400420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1060670030 (or 1060670028 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 19.

Adding to 21213400420 its reverse (2400431212), we get a palindrome (23613831632).

The spelling of 21213400420 in words is "twenty-one billion, two hundred thirteen million, four hundred thousand, four hundred twenty".