21208508064 has 72 divisors (see below), whose sum is σ = 60382288512. Its totient is φ = 7061228160.

The previous prime is 21208508039. The next prime is 21208508071. The reversal of 21208508064 is 46080580212.

It is a tau number, because it is divible by the number of its divisors (72).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 205879 + ... + 291209.

It is an arithmetic number, because the mean of its divisors is an integer number (838642896).

Almost surely, 2^21208508064 is an apocalyptic number.

21208508064 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21208508064 is an abundant number, since it is smaller than the sum of its proper divisors (39173780448).

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

21208508064 is a wasteful number, since it uses less digits than its factorization.

21208508064 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86210 (or 86199 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 36.

The spelling of 21208508064 in words is "twenty-one billion, two hundred eight million, five hundred eight thousand, sixty-four".