21052051666 has 16 divisors (see below), whose sum is σ = 32178987288. Its totient is φ = 10325785600.

The previous prime is 21052051627. The next prime is 21052051667. The reversal of 21052051666 is 66615025012.

It can be written as a sum of positive squares in 4 ways, for example, as 16159748641 + 4892303025 = 127121^2 + 69945^2 .

It is not an unprimeable number, because it can be changed into a prime (21052051667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 915186 + ... + 937906.

Almost surely, 2^21052051666 is an apocalyptic number.

21052051666 is a deficient number, since it is larger than the sum of its proper divisors (11126935622).

21052051666 is a wasteful number, since it uses less digits than its factorization.

21052051666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31517.

The product of its (nonzero) digits is 21600, while the sum is 34.

Adding to 21052051666 its reverse (66615025012), we get a palindrome (87667076678).

The spelling of 21052051666 in words is "twenty-one billion, fifty-two million, fifty-one thousand, six hundred sixty-six".