661870215 has 24 divisors (see below), whose sum is σ = 1171654848. Its totient is φ = 345485760.

The previous prime is 661870211. The next prime is 661870247. The reversal of 661870215 is 512078166.

It is not a de Polignac number, because 661870215 - 2² = 661870211 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 661870215.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661870211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 154356 + ... + 158585.

It is an arithmetic number, because the mean of its divisors is an integer number (48818952).

Almost surely, 2^661870215 is an apocalyptic number.

661870215 is a deficient number, since it is larger than the sum of its proper divisors (509784633).

661870215 is a wasteful number, since it uses less digits than its factorization.

661870215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312999 (or 312996 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 661870215 is about 25726.8384182744. The cubic root of 661870215 is about 871.4803769319.

The spelling of 661870215 in words is "six hundred sixty-one million, eight hundred seventy thousand, two hundred fifteen".