66361881664 has 63 divisors (see below), whose sum is σ = 142653420687. Its totient is φ = 30616195584.

The previous prime is 66361881631. The next prime is 66361881671. The reversal of 66361881664 is 46618816366.

The square root of 66361881664 is 257608.

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

It can be written as a sum of positive squares in 4 ways, for example, as 9527321664 + 56834560000 = 97608^2 + 238400^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 26789994 + ... + 26792470.

Almost surely, 2^66361881664 is an apocalyptic number.

66361881664 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

66361881664 is the 257608-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66361881664

66361881664 is an abundant number, since it is smaller than the sum of its proper divisors (76291539023).

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

66361881664 is an frugal number, since it uses more digits than its factorization.

66361881664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4992 (or 2492 counting only the distinct ones).

The product of its digits is 5971968, while the sum is 55.

The spelling of 66361881664 in words is "sixty-six billion, three hundred sixty-one million, eight hundred eighty-one thousand, six hundred sixty-four".