21208421437 has 16 divisors (see below), whose sum is σ = 25046354944. Its totient is φ = 17592066000.

The previous prime is 21208421413. The next prime is 21208421447. The reversal of 21208421437 is 73412480212.

It is not a de Polignac number, because 21208421437 - 2¹⁹ = 21207897149 is a prime.

It is a super-2 number, since 2×21208421437² (a number of 21 digits) 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 (21208421407) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 157687 + ... + 259387.

It is an arithmetic number, because the mean of its divisors is an integer number (1565397184).

Almost surely, 2^21208421437 is an apocalyptic number.

It is an amenable number.

21208421437 is a deficient number, since it is larger than the sum of its proper divisors (3837933507).

21208421437 is an frugal number, since it uses more digits than its factorization.

21208421437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101801 (or 101739 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 34.

The spelling of 21208421437 in words is "twenty-one billion, two hundred eight million, four hundred twenty-one thousand, four hundred thirty-seven".