261405816 has 64 divisors (see below), whose sum is σ = 755308800. Its totient is φ = 73843968.

The previous prime is 261405799. The next prime is 261405817. The reversal of 261405816 is 618504162.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261405817) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6211 + ... + 23693.

It is an arithmetic number, because the mean of its divisors is an integer number (11801700).

Almost surely, 2^261405816 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 261405816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (377654400).

261405816 is an abundant number, since it is smaller than the sum of its proper divisors (493902984).

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

261405816 is a wasteful number, since it uses less digits than its factorization.

261405816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17588 (or 17584 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 33.

The square root of 261405816 is about 16168.0492329780. The cubic root of 261405816 is about 639.3986995589.

Adding to 261405816 its reverse (618504162), we get a palindrome (879909978).

The spelling of 261405816 in words is "two hundred sixty-one million, four hundred five thousand, eight hundred sixteen".