66640440 has 32 divisors (see below), whose sum is σ = 199921680. Its totient is φ = 17770752.

The previous prime is 66640423. The next prime is 66640481. The reversal of 66640440 is 4404666.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 66640398 and 66640407.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 277549 + ... + 277788.

Almost surely, 2^66640440 is an apocalyptic number.

66640440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66640440 is an abundant number, since it is smaller than the sum of its proper divisors (133281240).

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

66640440 is a wasteful number, since it uses less digits than its factorization.

66640440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 555351 (or 555347 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 30.

The square root of 66640440 is about 8163.3596025166. The cubic root of 66640440 is about 405.4269541026.

The spelling of 66640440 in words is "sixty-six million, six hundred forty thousand, four hundred forty".