21687491280 has 320 divisors, whose sum is σ = 82937691648. Its totient is φ = 4565237760.

The previous prime is 21687491279. The next prime is 21687491291. The reversal of 21687491280 is 8219478612.

It is a happy number.

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 63 ways as a sum of consecutive naturals, for example, 12600820 + ... + 12602540.

Almost surely, 2^21687491280 is an apocalyptic number.

21687491280 is a gapful number since it is divisible by the number (20) 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 21687491280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41468845824).

21687491280 is an abundant number, since it is smaller than the sum of its proper divisors (61250200368).

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

21687491280 is a wasteful number, since it uses less digits than its factorization.

21687491280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2334 (or 2328 counting only the distinct ones).

The product of its (nonzero) digits is 387072, while the sum is 48.

The spelling of 21687491280 in words is "twenty-one billion, six hundred eighty-seven million, four hundred ninety-one thousand, two hundred eighty".