261637757920 has 288 divisors, whose sum is σ = 790917807456. Its totient is φ = 81546178560.

The previous prime is 261637757911. The next prime is 261637757999. The reversal of 261637757920 is 29757736162.

It is a Harshad number since it is a multiple of its sum of digits (55).

It is a congruent number.

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, 10422504 + ... + 10447576.

It is an arithmetic number, because the mean of its divisors is an integer number (2746242387).

Almost surely, 2^261637757920 is an apocalyptic number.

261637757920 is a gapful number since it is divisible by the number (20) 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 261637757920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (395458903728).

261637757920 is an abundant number, since it is smaller than the sum of its proper divisors (529280049536).

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

261637757920 is a wasteful number, since it uses less digits than its factorization.

261637757920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25135 (or 25098 counting only the distinct ones).

The product of its (nonzero) digits is 6667920, while the sum is 55.

The spelling of 261637757920 in words is "two hundred sixty-one billion, six hundred thirty-seven million, seven hundred fifty-seven thousand, nine hundred twenty".