1628738981 has 4 divisors (see below), whose sum is σ = 1668464364. Its totient is φ = 1589013600.

The previous prime is 1628738959. The next prime is 1628738999. The reversal of 1628738981 is 1898378261.

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 473758756 + 1154980225 = 21766^2 + 33985^2 .

It is a cyclic number.

It is not a de Polignac number, because 1628738981 - 2¹⁴ = 1628722597 is a prime.

It is a super-2 number, since 2×1628738981² = 5305581336457836722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1628738081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19862630 + ... + 19862711.

It is an arithmetic number, because the mean of its divisors is an integer number (417116091).

Almost surely, 2^1628738981 is an apocalyptic number.

It is an amenable number.

1628738981 is a deficient number, since it is larger than the sum of its proper divisors (39725383).

1628738981 is an equidigital number, since it uses as much as digits as its factorization.

1628738981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39725382.

The product of its digits is 1161216, while the sum is 53.

The square root of 1628738981 is about 40357.6384467674. The cubic root of 1628738981 is about 1176.5683552895.

The spelling of 1628738981 in words is "one billion, six hundred twenty-eight million, seven hundred thirty-eight thousand, nine hundred eighty-one".