1391716021 has 4 divisors (see below), whose sum is σ = 1392151852. Its totient is φ = 1391280192.

The previous prime is 1391715991. The next prime is 1391716031. The reversal of 1391716021 is 1206171931.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1206171931 = 5519 ⋅218549.

It can be written as a sum of positive squares in 2 ways, for example, as 1201662225 + 190053796 = 34665^2 + 13786^2 .

It is a cyclic number.

It is not a de Polignac number, because 1391716021 - 2⁵ = 1391715989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1391716031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 213090 + ... + 219523.

It is an arithmetic number, because the mean of its divisors is an integer number (348037963).

Almost surely, 2^1391716021 is an apocalyptic number.

It is an amenable number.

1391716021 is a deficient number, since it is larger than the sum of its proper divisors (435831).

1391716021 is an equidigital number, since it uses as much as digits as its factorization.

1391716021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 435830.

The product of its (nonzero) digits is 2268, while the sum is 31.

The square root of 1391716021 is about 37305.7103001672. The cubic root of 1391716021 is about 1116.4781005523.

Adding to 1391716021 its reverse (1206171931), we get a palindrome (2597887952).

The spelling of 1391716021 in words is "one billion, three hundred ninety-one million, seven hundred sixteen thousand, twenty-one".