21001452166566 has 48 divisors (see below), whose sum is σ = 48372286987440. Its totient is φ = 6566373777600.

The previous prime is 21001452166561. The next prime is 21001452166579. The reversal of 21001452166566 is 66566125410012.

21001452166566 is a `hidden beast` number, since 2 + 1 + 0 + 0 + 1 + 4 + 5 + 21 + 66 + 566 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001452166561) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 303964245 + ... + 304033328.

It is an arithmetic number, because the mean of its divisors is an integer number (1007755978905).

Almost surely, 2^{21001452166566} is an apocalyptic number.

21001452166566 is an abundant number, since it is smaller than the sum of its proper divisors (27370834820874).

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

21001452166566 is a wasteful number, since it uses less digits than its factorization.

21001452166566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 607997701 (or 607997698 counting only the distinct ones).

The product of its (nonzero) digits is 518400, while the sum is 45.

Adding to 21001452166566 its reverse (66566125410012), we get a palindrome (87567577576578).

The spelling of 21001452166566 in words is "twenty-one trillion, one billion, four hundred fifty-two million, one hundred sixty-six thousand, five hundred sixty-six".