661155501 has 4 divisors (see below), whose sum is σ = 881540672. Its totient is φ = 440770332.

The previous prime is 661155497. The next prime is 661155527. The reversal of 661155501 is 105551166.

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 not a de Polignac number, because 661155501 - 2² = 661155497 is a prime.

It is a super-2 number, since 2×661155501² = 874253193005122002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661155541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110192581 + ... + 110192586.

It is an arithmetic number, because the mean of its divisors is an integer number (220385168).

Almost surely, 2^661155501 is an apocalyptic number.

It is an amenable number.

661155501 is a deficient number, since it is larger than the sum of its proper divisors (220385171).

661155501 is a wasteful number, since it uses less digits than its factorization.

661155501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220385170.

The product of its (nonzero) digits is 4500, while the sum is 30.

The square root of 661155501 is about 25712.9442304844. The cubic root of 661155501 is about 871.1665774676.

The spelling of 661155501 in words is "six hundred sixty-one million, one hundred fifty-five thousand, five hundred one".