66891565 has 16 divisors (see below), whose sum is σ = 88080048. Its totient is φ = 48462336.

The previous prime is 66891551. The next prime is 66891589. The reversal of 66891565 is 56519866.

It can be written as a sum of positive squares in 8 ways, for example, as 16467364 + 50424201 = 4058^2 + 7101^2 .

It is not a de Polignac number, because 66891565 - 2⁷ = 66891437 is a prime.

It is a Duffinian number.

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, 6264 + ... + 13153.

It is an arithmetic number, because the mean of its divisors is an integer number (5505003).

Almost surely, 2^66891565 is an apocalyptic number.

66891565 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

66891565 is a deficient number, since it is larger than the sum of its proper divisors (21188483).

66891565 is a wasteful number, since it uses less digits than its factorization.

66891565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19488.

The product of its digits is 388800, while the sum is 46.

The square root of 66891565 is about 8178.7263678399. The cubic root of 66891565 is about 405.9355803055.

The spelling of 66891565 in words is "sixty-six million, eight hundred ninety-one thousand, five hundred sixty-five".