661611701521 has 8 divisors (see below), whose sum is σ = 664236900000. Its totient is φ = 658988423520.

The previous prime is 661611701507. The next prime is 661611701567. The reversal of 661611701521 is 125107116166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 661611701521 - 2²⁹ = 661074830609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661611701221) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 212230 + ... + 1169728.

It is an arithmetic number, because the mean of its divisors is an integer number (83029612500).

Almost surely, 2^661611701521 is an apocalyptic number.

It is an amenable number.

661611701521 is a deficient number, since it is larger than the sum of its proper divisors (2625198479).

661611701521 is a wasteful number, since it uses less digits than its factorization.

661611701521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 960239.

The product of its (nonzero) digits is 15120, while the sum is 37.

Adding to 661611701521 its reverse (125107116166), we get a palindrome (786718817687).

The spelling of 661611701521 in words is "six hundred sixty-one billion, six hundred eleven million, seven hundred one thousand, five hundred twenty-one".