261666401263344 has 480 divisors, whose sum is σ = 952930539684864. Its totient is φ = 64994294661120.

The previous prime is 261666401263327. The next prime is 261666401263387. The reversal of 261666401263344 is 443362104666162.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1053890064 + ... + 1054138320.

Almost surely, 2^{261666401263344} is an apocalyptic number.

261666401263344 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261666401263344, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (476465269842432).

261666401263344 is an abundant number, since it is smaller than the sum of its proper divisors (691264138421520).

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

261666401263344 is a wasteful number, since it uses less digits than its factorization.

261666401263344 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 252445 (or 252436 counting only the distinct ones).

The product of its (nonzero) digits is 17915904, while the sum is 54.

The spelling of 261666401263344 in words is "two hundred sixty-one trillion, six hundred sixty-six billion, four hundred one million, two hundred sixty-three thousand, three hundred forty-four".