661666501 has 2 divisors, whose sum is σ = 661666502. Its totient is φ = 661666500.

The previous prime is 661666471. The next prime is 661666513. The reversal of 661666501 is 105666166.

661666501 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 659154276 + 2512225 = 25674^2 + 1585^2 .

It is a cyclic number.

It is not a de Polignac number, because 661666501 - 2⁷ = 661666373 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661666531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330833250 + 330833251.

It is an arithmetic number, because the mean of its divisors is an integer number (330833251).

Almost surely, 2^661666501 is an apocalyptic number.

It is an amenable number.

661666501 is a deficient number, since it is larger than the sum of its proper divisors (1).

661666501 is an equidigital number, since it uses as much as digits as its factorization.

661666501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 38880, while the sum is 37.

The square root of 661666501 is about 25722.8789407407. The cubic root of 661666501 is about 871.3909581070.

The spelling of 661666501 in words is "six hundred sixty-one million, six hundred sixty-six thousand, five hundred one".