21172936837 has 6 divisors (see below), whose sum is σ = 22802189298. Its totient is φ = 19543765104.

The previous prime is 21172936789. The next prime is 21172936849. The reversal of 21172936837 is 73863927112.

It can be written as a sum of positive squares in 3 ways, for example, as 3391781121 + 17781155716 = 58239^2 + 133346^2 .

It is not a de Polignac number, because 21172936837 - 2¹⁵ = 21172904069 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 (21172936867) 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 5 ways as a sum of consecutive naturals, for example, 504463 + ... + 544819.

It is an arithmetic number, because the mean of its divisors is an integer number (3800364883).

Almost surely, 2^21172936837 is an apocalyptic number.

It is an amenable number.

21172936837 is a deficient number, since it is larger than the sum of its proper divisors (1629252461).

21172936837 is an frugal number, since it uses more digits than its factorization.

21172936837 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80727 (or 40370 counting only the distinct ones).

The product of its digits is 762048, while the sum is 49.

The spelling of 21172936837 in words is "twenty-one billion, one hundred seventy-two million, nine hundred thirty-six thousand, eight hundred thirty-seven".