21518466816 has 432 divisors, whose sum is σ = 73316154240. Its totient is φ = 5540290560.

The previous prime is 21518466803. The next prime is 21518466829. The reversal of 21518466816 is 61866481512.

It is an interprime number because it is at equal distance from previous prime (21518466803) and next prime (21518466829).

It is a super-2 number, since 2×21518466816² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 93966990 + ... + 93967218.

It is an arithmetic number, because the mean of its divisors is an integer number (169713320).

Almost surely, 2^21518466816 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 21518466816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36658077120).

21518466816 is an abundant number, since it is smaller than the sum of its proper divisors (51797687424).

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

21518466816 is a wasteful number, since it uses less digits than its factorization.

21518466816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 500 (or 479 counting only the distinct ones).

The product of its digits is 552960, while the sum is 48.

The spelling of 21518466816 in words is "twenty-one billion, five hundred eighteen million, four hundred sixty-six thousand, eight hundred sixteen".