668687749 has 4 divisors (see below), whose sum is σ = 669768640. Its totient is φ = 667606860.

The previous prime is 668687699. The next prime is 668687759. The reversal of 668687749 is 947786866.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 668687749 - 2¹⁷ = 668556677 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 (668687759) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 539517 + ... + 540754.

It is an arithmetic number, because the mean of its divisors is an integer number (167442160).

Almost surely, 2^668687749 is an apocalyptic number.

It is an amenable number.

668687749 is a deficient number, since it is larger than the sum of its proper divisors (1080891).

668687749 is a wasteful number, since it uses less digits than its factorization.

668687749 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1080890.

The product of its digits is 24385536, while the sum is 61.

The square root of 668687749 is about 25858.9974476970. The cubic root of 668687749 is about 874.4623631631.

The spelling of 668687749 in words is "six hundred sixty-eight million, six hundred eighty-seven thousand, seven hundred forty-nine".