1057660721 has 4 divisors (see below), whose sum is σ = 1139019252. Its totient is φ = 976302192.

The previous prime is 1057660717. The next prime is 1057660733. The reversal of 1057660721 is 1270667501.

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 238270096 + 819390625 = 15436^2 + 28625^2 .

It is a cyclic number.

It is not a de Polignac number, because 1057660721 - 2² = 1057660717 is a prime.

It is a super-2 number, since 2×1057660721² = 2237292401492479682, 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 (1057666721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40679246 + ... + 40679271.

It is an arithmetic number, because the mean of its divisors is an integer number (284754813).

Almost surely, 2^1057660721 is an apocalyptic number.

It is an amenable number.

1057660721 is a deficient number, since it is larger than the sum of its proper divisors (81358531).

1057660721 is an equidigital number, since it uses as much as digits as its factorization.

1057660721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81358530.

The product of its (nonzero) digits is 17640, while the sum is 35.

The square root of 1057660721 is about 32521.6961581034. The cubic root of 1057660721 is about 1018.8622200341.

The spelling of 1057660721 in words is "one billion, fifty-seven million, six hundred sixty thousand, seven hundred twenty-one".