21138646464 has 280 divisors, whose sum is σ = 71455074768. Its totient is φ = 6121267200.

The previous prime is 21138646411. The next prime is 21138646471. The reversal of 21138646464 is 46464683112.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1136439 + ... + 1154889.

Almost surely, 2^21138646464 is an apocalyptic number.

21138646464 is a gapful number since it is divisible by the number (24) 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 21138646464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35727537384).

21138646464 is an abundant number, since it is smaller than the sum of its proper divisors (50316428304).

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

21138646464 is a wasteful number, since it uses less digits than its factorization.

21138646464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18505 (or 18486 counting only the distinct ones).

The product of its digits is 663552, while the sum is 45.

The spelling of 21138646464 in words is "twenty-one billion, one hundred thirty-eight million, six hundred forty-six thousand, four hundred sixty-four".