501555661 has 2 divisors, whose sum is σ = 501555662. Its totient is φ = 501555660.

The previous prime is 501555647. The next prime is 501555671. The reversal of 501555661 is 166555105.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 257602500 + 243953161 = 16050^2 + 15619^2 .

It is a cyclic number.

It is not a de Polignac number, because 501555661 - 2¹⁷ = 501424589 is a prime.

It is a super-2 number, since 2×501555661² = 503116162162293842, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (501555671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 250777830 + 250777831.

It is an arithmetic number, because the mean of its divisors is an integer number (250777831).

Almost surely, 2^501555661 is an apocalyptic number.

It is an amenable number.

501555661 is a deficient number, since it is larger than the sum of its proper divisors (1).

501555661 is an equidigital number, since it uses as much as digits as its factorization.

501555661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 22500, while the sum is 34.

The square root of 501555661 is about 22395.4383971379. The cubic root of 501555661 is about 794.5228263950.

The spelling of 501555661 in words is "five hundred one million, five hundred fifty-five thousand, six hundred sixty-one".