21139197408 has 216 divisors, whose sum is σ = 70719143040. Its totient is φ = 5971553280.

The previous prime is 21139197341. The next prime is 21139197427. The reversal of 21139197408 is 80479193112.

21139197408 is a `hidden beast` number, since 21 + 1 + 39 + 197 + 408 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1247553 + ... + 1264383.

It is an arithmetic number, because the mean of its divisors is an integer number (327403440).

Almost surely, 2^21139197408 is an apocalyptic number.

21139197408 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21139197408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35359571520).

21139197408 is an abundant number, since it is smaller than the sum of its proper divisors (49579945632).

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

21139197408 is a wasteful number, since it uses less digits than its factorization.

21139197408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16950 (or 16932 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The spelling of 21139197408 in words is "twenty-one billion, one hundred thirty-nine million, one hundred ninety-seven thousand, four hundred eight".