66621645 has 24 divisors (see below), whose sum is σ = 118601496. Its totient is φ = 34570368.

The previous prime is 66621641. The next prime is 66621647. The reversal of 66621645 is 54612666.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 16112196 + 50509449 = 4014^2 + 7107^2 .

It is not a de Polignac number, because 66621645 - 2² = 66621641 is a prime.

It is a super-3 number, since 3×66621645³ (a number of 24 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66621641) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 18342 + ... + 21671.

It is an arithmetic number, because the mean of its divisors is an integer number (4941729).

Almost surely, 2^66621645 is an apocalyptic number.

It is an amenable number.

66621645 is a deficient number, since it is larger than the sum of its proper divisors (51979851).

66621645 is a wasteful number, since it uses less digits than its factorization.

66621645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40061 (or 40058 counting only the distinct ones).

The product of its digits is 51840, while the sum is 36.

The square root of 66621645 is about 8162.2083408842. The cubic root of 66621645 is about 405.3888355264.

The spelling of 66621645 in words is "sixty-six million, six hundred twenty-one thousand, six hundred forty-five".