670720921 has 4 divisors (see below), whose sum is σ = 722314852. Its totient is φ = 619126992.

The previous prime is 670720877. The next prime is 670720951. The reversal of 670720921 is 129027076.

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

It can be written as a sum of positive squares in 2 ways, for example, as 68558400 + 602162521 = 8280^2 + 24539^2 .

It is a cyclic number.

It is not a de Polignac number, because 670720921 - 2¹⁷ = 670589849 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (670720951) 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, 25796946 + ... + 25796971.

It is an arithmetic number, because the mean of its divisors is an integer number (180578713).

Almost surely, 2^670720921 is an apocalyptic number.

It is an amenable number.

670720921 is a deficient number, since it is larger than the sum of its proper divisors (51593931).

670720921 is a wasteful number, since it uses less digits than its factorization.

670720921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51593930.

The product of its (nonzero) digits is 10584, while the sum is 34.

The square root of 670720921 is about 25898.2802710914. The cubic root of 670720921 is about 875.3477457521.

Adding to 670720921 its reverse (129027076), we get a palindrome (799747997).

The spelling of 670720921 in words is "six hundred seventy million, seven hundred twenty thousand, nine hundred twenty-one".