661012501 has 2 divisors, whose sum is σ = 661012502. Its totient is φ = 661012500.

The previous prime is 661012477. The next prime is 661012519. The reversal of 661012501 is 105210166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 493284100 + 167728401 = 22210^2 + 12951^2 .

It is a cyclic number.

It is not a de Polignac number, because 661012501 - 2²³ = 652623893 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661012301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330506250 + 330506251.

It is an arithmetic number, because the mean of its divisors is an integer number (330506251).

Almost surely, 2^661012501 is an apocalyptic number.

It is an amenable number.

661012501 is a deficient number, since it is larger than the sum of its proper divisors (1).

661012501 is an equidigital number, since it uses as much as digits as its factorization.

661012501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 661012501 is about 25710.1633794887. The cubic root of 661012501 is about 871.1037653137.

Adding to 661012501 its reverse (105210166), we get a palindrome (766222667).

The spelling of 661012501 in words is "six hundred sixty-one million, twelve thousand, five hundred one".