21503121408 has 384 divisors, whose sum is σ = 68062176000. Its totient is φ = 6688604160.

The previous prime is 21503121401. The next prime is 21503121439. The reversal of 21503121408 is 80412130512.

21503121408 is a `hidden beast` number, since 2 + 1 + 503 + 12 + 140 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21503121401) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 101910423 + ... + 101910633.

It is an arithmetic number, because the mean of its divisors is an integer number (177245250).

Almost surely, 2^21503121408 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21503121408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34031088000).

21503121408 is an abundant number, since it is smaller than the sum of its proper divisors (46559054592).

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

21503121408 is a wasteful number, since it uses less digits than its factorization.

21503121408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 358 (or 332 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The spelling of 21503121408 in words is "twenty-one billion, five hundred three million, one hundred twenty-one thousand, four hundred eight".