21394566720 has 448 divisors, whose sum is σ = 78931008000. Its totient is φ = 5448425472.

The previous prime is 21394566689. The next prime is 21394566727. The reversal of 21394566720 is 2766549312.

21394566720 is a `hidden beast` number, since 2 + 13 + 9 + 4 + 566 + 72 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (21394566727) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 25807266 + ... + 25808094.

Almost surely, 2^21394566720 is an apocalyptic number.

21394566720 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 21394566720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39465504000).

21394566720 is an abundant number, since it is smaller than the sum of its proper divisors (57536441280).

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

21394566720 is a wasteful number, since it uses less digits than its factorization.

21394566720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 987 (or 971 counting only the distinct ones).

The product of its (nonzero) digits is 544320, while the sum is 45.

The spelling of 21394566720 in words is "twenty-one billion, three hundred ninety-four million, five hundred sixty-six thousand, seven hundred twenty".