21018678408 has 384 divisors, whose sum is σ = 74474400000. Its totient is φ = 5200091136.

The previous prime is 21018678407. The next prime is 21018678469. The reversal of 21018678408 is 80487681012.

It is not an unprimeable number, because it can be changed into a prime (21018678407) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 13568418 + ... + 13569966.

It is an arithmetic number, because the mean of its divisors is an integer number (193943750).

Almost surely, 2^21018678408 is an apocalyptic number.

21018678408 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 21018678408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37237200000).

21018678408 is an abundant number, since it is smaller than the sum of its proper divisors (53455721592).

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

21018678408 is a wasteful number, since it uses less digits than its factorization.

21018678408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1709 (or 1702 counting only the distinct ones).

The product of its (nonzero) digits is 172032, while the sum is 45.

The spelling of 21018678408 in words is "twenty-one billion, eighteen million, six hundred seventy-eight thousand, four hundred eight".