265021661 has 4 divisors (see below), whose sum is σ = 265131132. Its totient is φ = 264912192.

The previous prime is 265021651. The next prime is 265021667. The reversal of 265021661 is 166120562.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166120562 = 2 ⋅83060281.

It can be written as a sum of positive squares in 2 ways, for example, as 221712100 + 43309561 = 14890^2 + 6581^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-265021661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (265021667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 51020 + ... + 55973.

It is an arithmetic number, because the mean of its divisors is an integer number (66282783).

Almost surely, 2^265021661 is an apocalyptic number.

It is an amenable number.

265021661 is a deficient number, since it is larger than the sum of its proper divisors (109471).

265021661 is a wasteful number, since it uses less digits than its factorization.

265021661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 109470.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 265021661 is about 16279.4858948310. The cubic root of 265021661 is about 642.3333292639. Note that the first 4 decimals are identical.

The spelling of 265021661 in words is "two hundred sixty-five million, twenty-one thousand, six hundred sixty-one".