666721606 has 32 divisors (see below), whose sum is σ = 1084752000. Its totient is φ = 306189312.

The previous prime is 666721603. The next prime is 666721633. The reversal of 666721606 is 606127666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666721603) 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, 237660 + ... + 240448.

It is an arithmetic number, because the mean of its divisors is an integer number (33898500).

Almost surely, 2^666721606 is an apocalyptic number.

666721606 is a deficient number, since it is larger than the sum of its proper divisors (418030394).

666721606 is a wasteful number, since it uses less digits than its factorization.

666721606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2976.

The product of its (nonzero) digits is 108864, while the sum is 40.

The square root of 666721606 is about 25820.9528484136. The cubic root of 666721606 is about 873.6044610413.

The spelling of 666721606 in words is "six hundred sixty-six million, seven hundred twenty-one thousand, six hundred six".