21208421406 has 16 divisors (see below), whose sum is σ = 43785128448. Its totient is φ = 6841426200.

The previous prime is 21208421393. The next prime is 21208421407. The reversal of 21208421406 is 60412480212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21208421407) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 57011700 + ... + 57012071.

It is an arithmetic number, because the mean of its divisors is an integer number (2736570528).

Almost surely, 2^21208421406 is an apocalyptic number.

21208421406 is an abundant number, since it is smaller than the sum of its proper divisors (22576707042).

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

21208421406 is a wasteful number, since it uses less digits than its factorization.

21208421406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 114023807.

The product of its (nonzero) digits is 6144, while the sum is 30.

The spelling of 21208421406 in words is "twenty-one billion, two hundred eight million, four hundred twenty-one thousand, four hundred six".