661765215 has 64 divisors (see below), whose sum is σ = 1133862912. Its totient is φ = 329011200.

The previous prime is 661765213. The next prime is 661765241. The reversal of 661765215 is 512567166.

It is not a de Polignac number, because 661765215 - 2¹ = 661765213 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661765213) 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 63 ways as a sum of consecutive naturals, for example, 1963527 + ... + 1963863.

It is an arithmetic number, because the mean of its divisors is an integer number (17716608).

Almost surely, 2^661765215 is an apocalyptic number.

661765215 is a deficient number, since it is larger than the sum of its proper divisors (472097697).

661765215 is a wasteful number, since it uses less digits than its factorization.

661765215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 520.

The product of its digits is 75600, while the sum is 39.

The square root of 661765215 is about 25724.7976668428. The cubic root of 661765215 is about 871.4342902134.

The spelling of 661765215 in words is "six hundred sixty-one million, seven hundred sixty-five thousand, two hundred fifteen".