661989065 has 8 divisors (see below), whose sum is σ = 794583240. Its totient is φ = 529460352.

The previous prime is 661989007. The next prime is 661989071. The reversal of 661989065 is 560989166.

It can be written as a sum of positive squares in 4 ways, for example, as 46403344 + 615585721 = 6812^2 + 24811^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 661989065 - 2¹⁴ = 661972681 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9647 + ... + 37643.

It is an arithmetic number, because the mean of its divisors is an integer number (99322905).

Almost surely, 2^661989065 is an apocalyptic number.

It is an amenable number.

661989065 is a deficient number, since it is larger than the sum of its proper divisors (132594175).

661989065 is a wasteful number, since it uses less digits than its factorization.

661989065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32731.

The product of its (nonzero) digits is 699840, while the sum is 50.

The square root of 661989065 is about 25729.1481592376. The cubic root of 661989065 is about 871.5325368275.

The spelling of 661989065 in words is "six hundred sixty-one million, nine hundred eighty-nine thousand, sixty-five".