966639721 has 4 divisors (see below), whose sum is σ = 966703744. Its totient is φ = 966575700.

The previous prime is 966639697. The next prime is 966639743. The reversal of 966639721 is 127936669.

966639721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 966639721 - 2⁷ = 966639593 is a prime.

It is a super-5 number, since 5×966639721⁵ (a number of 46 digits) contains 55555 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (966639781) 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, 4576 + ... + 44206.

It is an arithmetic number, because the mean of its divisors is an integer number (241675936).

Almost surely, 2^966639721 is an apocalyptic number.

It is an amenable number.

966639721 is a deficient number, since it is larger than the sum of its proper divisors (64023).

966639721 is a wasteful number, since it uses less digits than its factorization.

966639721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64022.

The product of its digits is 734832, while the sum is 49.

The square root of 966639721 is about 31090.8301754714. The cubic root of 966639721 is about 988.7539064960.

The spelling of 966639721 in words is "nine hundred sixty-six million, six hundred thirty-nine thousand, seven hundred twenty-one".