670905721 has 2 divisors, whose sum is σ = 670905722. Its totient is φ = 670905720.

The previous prime is 670905709. The next prime is 670905769. The reversal of 670905721 is 127509076.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 641355625 + 29550096 = 25325^2 + 5436^2 .

It is a cyclic number.

It is not a de Polignac number, because 670905721 - 2⁷ = 670905593 is a prime.

It is a super-2 number, since 2×670905721² = 900228972941059682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (670905121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 335452860 + 335452861.

It is an arithmetic number, because the mean of its divisors is an integer number (335452861).

Almost surely, 2^670905721 is an apocalyptic number.

It is an amenable number.

670905721 is a deficient number, since it is larger than the sum of its proper divisors (1).

670905721 is an equidigital number, since it uses as much as digits as its factorization.

670905721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 26460, while the sum is 37.

The square root of 670905721 is about 25901.8478298364. The cubic root of 670905721 is about 875.4281315996.

The spelling of 670905721 in words is "six hundred seventy million, nine hundred five thousand, seven hundred twenty-one".