28420821637 has 6 divisors (see below), whose sum is σ = 30607693298. Its totient is φ = 26234043504.

The previous prime is 28420821613. The next prime is 28420821641. The reversal of 28420821637 is 73612802482.

It can be written as a sum of positive squares in 3 ways, for example, as 11657304961 + 16763516676 = 107969^2 + 129474^2 .

It is a de Polignac number, because none of the positive numbers 2^k-28420821637 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 28420821593 and 28420821602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28420821437) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 584463 + ... + 631219.

Almost surely, 2^28420821637 is an apocalyptic number.

It is an amenable number.

28420821637 is a deficient number, since it is larger than the sum of its proper divisors (2186871661).

28420821637 is an frugal number, since it uses more digits than its factorization.

28420821637 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93527 (or 46770 counting only the distinct ones).

The product of its (nonzero) digits is 258048, while the sum is 43.

The spelling of 28420821637 in words is "twenty-eight billion, four hundred twenty million, eight hundred twenty-one thousand, six hundred thirty-seven".