21237996820 has 12 divisors (see below), whose sum is σ = 44599793364. Its totient is φ = 8495198720.

The previous prime is 21237996797. The next prime is 21237996823. The reversal of 21237996820 is 2869973212.

It can be written as a sum of positive squares in 2 ways, for example, as 7082232336 + 14155764484 = 84156^2 + 118978^2 .

It is a super-2 number, since 2×21237996820² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21237996823) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 530949901 + ... + 530949940.

It is an arithmetic number, because the mean of its divisors is an integer number (3716649447).

Almost surely, 2^21237996820 is an apocalyptic number.

21237996820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21237996820 is an abundant number, since it is smaller than the sum of its proper divisors (23361796544).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21237996820 is a wasteful number, since it uses less digits than its factorization.

21237996820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1061899850 (or 1061899848 counting only the distinct ones).

The product of its (nonzero) digits is 653184, while the sum is 49.

The spelling of 21237996820 in words is "twenty-one billion, two hundred thirty-seven million, nine hundred ninety-six thousand, eight hundred twenty".