261564643 has 2 divisors, whose sum is σ = 261564644. Its totient is φ = 261564642.

The previous prime is 261564629. The next prime is 261564683. The reversal of 261564643 is 346465162.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 261564643 - 2⁹ = 261564131 is a prime.

It is not a weakly prime, because it can be changed into another prime (261564613) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130782321 + 130782322.

It is an arithmetic number, because the mean of its divisors is an integer number (130782322).

Almost surely, 2^261564643 is an apocalyptic number.

261564643 is a deficient number, since it is larger than the sum of its proper divisors (1).

261564643 is an equidigital number, since it uses as much as digits as its factorization.

261564643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 103680, while the sum is 37.

The square root of 261564643 is about 16172.9602423304. The cubic root of 261564643 is about 639.5281703030.

The spelling of 261564643 in words is "two hundred sixty-one million, five hundred sixty-four thousand, six hundred forty-three".