261213604128 has 144 divisors (see below), whose sum is σ = 746794634040. Its totient is φ = 86607286272.

The previous prime is 261213604117. The next prime is 261213604139. The reversal of 261213604128 is 821406312162.

It is a happy number.

261213604128 is a `hidden beast` number, since 2 + 6 + 1 + 21 + 3 + 604 + 1 + 28 = 666.

It is an interprime number because it is at equal distance from previous prime (261213604117) and next prime (261213604139).

It can be written as a sum of positive squares in 4 ways, for example, as 129435891984 + 131777712144 = 359772^2 + 363012^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 261213604092 and 261213604101.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 45880450 + ... + 45886142.

Almost surely, 2^261213604128 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261213604128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (373397317020).

261213604128 is an abundant number, since it is smaller than the sum of its proper divisors (485581029912).

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

261213604128 is a wasteful number, since it uses less digits than its factorization.

261213604128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6531 (or 6520 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The spelling of 261213604128 in words is "two hundred sixty-one billion, two hundred thirteen million, six hundred four thousand, one hundred twenty-eight".