21706985664 has 896 divisors, whose sum is σ = 83532431360. Its totient is φ = 5374771200.

The previous prime is 21706985659. The next prime is 21706985683. The reversal of 21706985664 is 46658960712.

21706985664 is a `hidden beast` number, since 2 + 1 + 70 + 6 + 9 + 8 + 566 + 4 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a self number, because there is not a number n which added to its sum of digits gives 21706985664.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 297355932 + ... + 297356004.

It is an arithmetic number, because the mean of its divisors is an integer number (93228160).

Almost surely, 2^21706985664 is an apocalyptic number.

21706985664 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 21706985664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41766215680).

21706985664 is an abundant number, since it is smaller than the sum of its proper divisors (61825445696).

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

21706985664 is a wasteful number, since it uses less digits than its factorization.

21706985664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206 (or 190 counting only the distinct ones).

The product of its (nonzero) digits is 4354560, while the sum is 54.

The spelling of 21706985664 in words is "twenty-one billion, seven hundred six million, nine hundred eighty-five thousand, six hundred sixty-four".