66401555 has 16 divisors (see below), whose sum is σ = 87084288. Its totient is φ = 48204000.

The previous prime is 66401539. The next prime is 66401557. The reversal of 66401555 is 55510466.

It is not a de Polignac number, because 66401555 - 2⁴ = 66401539 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66401557) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 56120 + ... + 57290.

It is an arithmetic number, because the mean of its divisors is an integer number (5442768).

Almost surely, 2^66401555 is an apocalyptic number.

66401555 is a deficient number, since it is larger than the sum of its proper divisors (20682733).

66401555 is a wasteful number, since it uses less digits than its factorization.

66401555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2218.

The product of its (nonzero) digits is 18000, while the sum is 32.

The square root of 66401555 is about 8148.7149293616. The cubic root of 66401555 is about 404.9419314195.

The spelling of 66401555 in words is "sixty-six million, four hundred one thousand, five hundred fifty-five".