661864911 has 16 divisors (see below), whose sum is σ = 923793408. Its totient is φ = 420991200.

The previous prime is 661864877. The next prime is 661864933. The reversal of 661864911 is 119468166.

It is not a de Polignac number, because 661864911 - 2¹⁰ = 661863887 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661864711) 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 15 ways as a sum of consecutive naturals, for example, 43516 + ... + 56721.

It is an arithmetic number, because the mean of its divisors is an integer number (57737088).

Almost surely, 2^661864911 is an apocalyptic number.

661864911 is a deficient number, since it is larger than the sum of its proper divisors (261928497).

661864911 is a wasteful number, since it uses less digits than its factorization.

661864911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100342.

The product of its digits is 62208, while the sum is 42.

The square root of 661864911 is about 25726.7353350556. The cubic root of 661864911 is about 871.4780490112.

The spelling of 661864911 in words is "six hundred sixty-one million, eight hundred sixty-four thousand, nine hundred eleven".