261646665605640 has 192 divisors, whose sum is σ = 973156305139200. Its totient is φ = 59723362423296.

The previous prime is 261646665605629. The next prime is 261646665605651. The reversal of 261646665605640 is 46506566646162.

It is an interprime number because it is at equal distance from previous prime (261646665605629) and next prime (261646665605651).

It is a Harshad number since it is a multiple of its sum of digits (63).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 68976880 + ... + 72671199.

It is an arithmetic number, because the mean of its divisors is an integer number (5068522422600).

Almost surely, 2^{261646665605640} is an apocalyptic number.

261646665605640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261646665605640 is an abundant number, since it is smaller than the sum of its proper divisors (711509639533560).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261646665605640 is a wasteful number, since it uses less digits than its factorization.

261646665605640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141648836 (or 141648829 counting only the distinct ones).

The product of its (nonzero) digits is 223948800, while the sum is 63.

The spelling of 261646665605640 in words is "two hundred sixty-one trillion, six hundred forty-six billion, six hundred sixty-five million, six hundred five thousand, six hundred forty".