261663540 has 48 divisors (see below), whose sum is σ = 733810560. Its totient is φ = 69667200.

The previous prime is 261663539. The next prime is 261663551. The reversal of 261663540 is 45366162.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 39465 + ... + 45615.

It is an arithmetic number, because the mean of its divisors is an integer number (15287720).

Almost surely, 2^261663540 is an apocalyptic number.

261663540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261663540 is an abundant number, since it is smaller than the sum of its proper divisors (472147020).

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

261663540 is a wasteful number, since it uses less digits than its factorization.

261663540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6872 (or 6870 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 33.

The square root of 261663540 is about 16176.0174332250. The cubic root of 261663540 is about 639.6087615317.

The spelling of 261663540 in words is "two hundred sixty-one million, six hundred sixty-three thousand, five hundred forty".