405665261 has 4 divisors (see below), whose sum is σ = 405769500. Its totient is φ = 405561024.

The previous prime is 405665251. The next prime is 405665269. The reversal of 405665261 is 162566504.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 85470025 + 320195236 = 9245^2 + 17894^2 .

It is a cyclic number.

It is not a de Polignac number, because 405665261 - 2²⁶ = 338556397 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (405665269) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46046 + ... + 54143.

It is an arithmetic number, because the mean of its divisors is an integer number (101442375).

Almost surely, 2^405665261 is an apocalyptic number.

It is an amenable number.

405665261 is a deficient number, since it is larger than the sum of its proper divisors (104239).

405665261 is a wasteful number, since it uses less digits than its factorization.

405665261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104238.

The product of its (nonzero) digits is 43200, while the sum is 35.

The square root of 405665261 is about 20141.1335579704. The cubic root of 405665261 is about 740.2685055571.

The spelling of 405665261 in words is "four hundred five million, six hundred sixty-five thousand, two hundred sixty-one".