661557061 has 8 divisors (see below), whose sum is σ = 730394784. Its totient is φ = 594168720.

The previous prime is 661557059. The next prime is 661557103. The reversal of 661557061 is 160755166.

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 661557061 - 2¹ = 661557059 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 661557061.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661557041) 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 7 ways as a sum of consecutive naturals, for example, 361386 + ... + 363211.

It is an arithmetic number, because the mean of its divisors is an integer number (91299348).

Almost surely, 2^661557061 is an apocalyptic number.

It is an amenable number.

661557061 is a deficient number, since it is larger than the sum of its proper divisors (68837723).

661557061 is a wasteful number, since it uses less digits than its factorization.

661557061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 724691.

The product of its (nonzero) digits is 37800, while the sum is 37.

The square root of 661557061 is about 25720.7515636694. The cubic root of 661557061 is about 871.3429126115.

The spelling of 661557061 in words is "six hundred sixty-one million, five hundred fifty-seven thousand, sixty-one".