661500001 has 4 divisors (see below), whose sum is σ = 667682352. Its totient is φ = 655317652.

The previous prime is 661499999. The next prime is 661500013. The reversal of 661500001 is 100005166.

661500001 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 661500001 - 2¹ = 661499999 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661500031) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3091015 + ... + 3091228.

It is an arithmetic number, because the mean of its divisors is an integer number (166920588).

Almost surely, 2^661500001 is an apocalyptic number.

It is an amenable number.

661500001 is a deficient number, since it is larger than the sum of its proper divisors (6182351).

661500001 is a wasteful number, since it uses less digits than its factorization.

661500001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6182350.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 661500001 is about 25719.6423186638. The cubic root of 661500001 is about 871.3178604736.

Adding to 661500001 its reverse (100005166), we get a palindrome (761505167).

The spelling of 661500001 in words is "six hundred sixty-one million, five hundred thousand, one".