7666721 has 4 divisors (see below), whose sum is σ = 7674672. Its totient is φ = 7658772.

The previous prime is 7666717. The next prime is 7666741. The reversal of 7666721 is 1276667.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 7666721 - 2² = 7666717 is a prime.

It is a super-2 number, since 2×7666721² = 117557221783682, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (7666741) 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, 2291 + ... + 4536.

It is an arithmetic number, because the mean of its divisors is an integer number (1918668).

Almost surely, 2^7666721 is an apocalyptic number.

It is an amenable number.

7666721 is a deficient number, since it is larger than the sum of its proper divisors (7951).

7666721 is a wasteful number, since it uses less digits than its factorization.

7666721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7950.

The product of its digits is 21168, while the sum is 35.

The square root of 7666721 is about 2768.8844324023. The cubic root of 7666721 is about 197.1831891307.

The spelling of 7666721 in words is "seven million, six hundred sixty-six thousand, seven hundred twenty-one".