661534751 has 4 divisors (see below), whose sum is σ = 671408472. Its totient is φ = 651661032.

The previous prime is 661534739. The next prime is 661534771. The reversal of 661534751 is 157435166.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 661534751 - 2¹⁰ = 661533727 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661534771) 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 3 ways as a sum of consecutive naturals, for example, 4936760 + ... + 4936893.

It is an arithmetic number, because the mean of its divisors is an integer number (167852118).

Almost surely, 2^661534751 is an apocalyptic number.

661534751 is a deficient number, since it is larger than the sum of its proper divisors (9873721).

661534751 is an equidigital number, since it uses as much as digits as its factorization.

661534751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9873720.

The product of its digits is 75600, while the sum is 38.

The square root of 661534751 is about 25720.3178635102. The cubic root of 661534751 is about 871.3331175991. Note that the first 3 decimals are identical.

The spelling of 661534751 in words is "six hundred sixty-one million, five hundred thirty-four thousand, seven hundred fifty-one".