661510501 has 2 divisors, whose sum is σ = 661510502. Its totient is φ = 661510500.

The previous prime is 661510469. The next prime is 661510513. The reversal of 661510501 is 105015166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 659154276 + 2356225 = 25674^2 + 1535^2 .

It is a cyclic number.

It is not a de Polignac number, because 661510501 - 2⁵ = 661510469 is a prime.

It is a super-3 number, since 3×661510501³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (662510501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330755250 + 330755251.

It is an arithmetic number, because the mean of its divisors is an integer number (330755251).

Almost surely, 2^661510501 is an apocalyptic number.

It is an amenable number.

661510501 is a deficient number, since it is larger than the sum of its proper divisors (1).

661510501 is an equidigital number, since it uses as much as digits as its factorization.

661510501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 900, while the sum is 25.

The square root of 661510501 is about 25719.8464419988. The cubic root of 661510501 is about 871.3224705966.

Adding to 661510501 its reverse (105015166), we get a palindrome (766525667).

The spelling of 661510501 in words is "six hundred sixty-one million, five hundred ten thousand, five hundred one".