661957787 has 16 divisors (see below), whose sum is σ = 713359104. Its totient is φ = 613008000.

The previous prime is 661957771. The next prime is 661957817. The reversal of 661957787 is 787759166.

It is a cyclic number.

It is not a de Polignac number, because 661957787 - 2⁴ = 661957771 is a prime.

It is a super-2 number, since 2×661957787² = 876376223539874738, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (661957717) 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, 65237 + ... + 74697.

It is an arithmetic number, because the mean of its divisors is an integer number (44584944).

Almost surely, 2^661957787 is an apocalyptic number.

661957787 is a deficient number, since it is larger than the sum of its proper divisors (51401317).

661957787 is a wasteful number, since it uses less digits than its factorization.

661957787 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9590.

The product of its digits is 4445280, while the sum is 56.

The square root of 661957787 is about 25728.5403200415. The cubic root of 661957787 is about 871.5188104054.

The spelling of 661957787 in words is "six hundred sixty-one million, nine hundred fifty-seven thousand, seven hundred eighty-seven".