661740261 has 64 divisors (see below), whose sum is σ = 1119928320. Its totient is φ = 338307840.

The previous prime is 661740257. The next prime is 661740329. The reversal of 661740261 is 162047166.

It is not a de Polignac number, because 661740261 - 2² = 661740257 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661740221) 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 63 ways as a sum of consecutive naturals, for example, 1315336 + ... + 1315838.

It is an arithmetic number, because the mean of its divisors is an integer number (17498880).

Almost surely, 2^661740261 is an apocalyptic number.

661740261 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

661740261 is a deficient number, since it is larger than the sum of its proper divisors (458188059).

661740261 is a wasteful number, since it uses less digits than its factorization.

661740261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 666.

The product of its (nonzero) digits is 12096, while the sum is 33.

The square root of 661740261 is about 25724.3126438784. The cubic root of 661740261 is about 871.4233366586.

The spelling of 661740261 in words is "six hundred sixty-one million, seven hundred forty thousand, two hundred sixty-one".