66405721554 has 24 divisors (see below), whose sum is σ = 143884746252. Its totient is φ = 22134366240.

The previous prime is 66405721549. The next prime is 66405721583. The reversal of 66405721554 is 45512750466.

66405721554 is a `hidden beast` number, since 6 + 6 + 40 + 57 + 2 + 1 + 554 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 64956168225 + 1449553329 = 254865^2 + 38073^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 530632 + ... + 643724.

Almost surely, 2^66405721554 is an apocalyptic number.

66405721554 is an abundant number, since it is smaller than the sum of its proper divisors (77479024698).

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

66405721554 is a wasteful number, since it uses less digits than its factorization.

66405721554 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145722 (or 145719 counting only the distinct ones).

The product of its (nonzero) digits is 1008000, while the sum is 45.

The spelling of 66405721554 in words is "sixty-six billion, four hundred five million, seven hundred twenty-one thousand, five hundred fifty-four".