21666662416 has 75 divisors (see below), whose sum is σ = 49038067743. Its totient is φ = 9273348000.

The previous prime is 21666662359. The next prime is 21666662431. The reversal of 21666662416 is 61426666612.

The square root of 21666662416 is 147196.

It is a perfect power (a square), and thus also a powerful number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 28850041 + ... + 28850791.

Almost surely, 2^21666662416 is an apocalyptic number.

21666662416 is the 147196-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21666662416

21666662416 is an abundant number, since it is smaller than the sum of its proper divisors (27371405327).

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

21666662416 is an frugal number, since it uses more digits than its factorization.

21666662416 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1538 (or 760 counting only the distinct ones).

The product of its digits is 746496, while the sum is 46.

The spelling of 21666662416 in words is "twenty-one billion, six hundred sixty-six million, six hundred sixty-two thousand, four hundred sixteen".