21387703806 has 56 divisors (see below), whose sum is σ = 54971831664. Its totient is φ = 6110769600.

The previous prime is 21387703801. The next prime is 21387703807. The reversal of 21387703806 is 60830778312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387703801) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 1037595 + ... + 1058006.

Almost surely, 2^21387703806 is an apocalyptic number.

21387703806 is an abundant number, since it is smaller than the sum of its proper divisors (33584127858).

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

21387703806 is an equidigital number, since it uses as much as digits as its factorization.

21387703806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2095628 (or 2095613 counting only the distinct ones).

The product of its (nonzero) digits is 338688, while the sum is 45.

The spelling of 21387703806 in words is "twenty-one billion, three hundred eighty-seven million, seven hundred three thousand, eight hundred six".