261551501064 has 768 divisors, whose sum is σ = 901002009600. Its totient is φ = 70006809600.

The previous prime is 261551501059. The next prime is 261551501069. The reversal of 261551501064 is 460105155162.

261551501064 is a `hidden beast` number, since 26 + 15 + 515 + 0 + 106 + 4 = 666.

It is an interprime number because it is at equal distance from previous prime (261551501059) and next prime (261551501069).

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

It is not an unprimeable number, because it can be changed into a prime (261551501069) by changing a digit.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 1996576279 + ... + 1996576409.

It is an arithmetic number, because the mean of its divisors is an integer number (1173179700).

Almost surely, 2^261551501064 is an apocalyptic number.

261551501064 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 261551501064, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (450501004800).

261551501064 is an abundant number, since it is smaller than the sum of its proper divisors (639450508536).

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

261551501064 is a wasteful number, since it uses less digits than its factorization.

261551501064 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351 (or 334 counting only the distinct ones).

The product of its (nonzero) digits is 36000, while the sum is 36.

The spelling of 261551501064 in words is "two hundred sixty-one billion, five hundred fifty-one million, five hundred one thousand, sixty-four".