21287020716 has 72 divisors (see below), whose sum is σ = 58208142720. Its totient is φ = 6520449024.

The previous prime is 21287020673. The next prime is 21287020721. The reversal of 21287020716 is 61702078212.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2380 + ... + 206348.

Almost surely, 2^21287020716 is an apocalyptic number.

21287020716 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21287020716, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29104071360).

21287020716 is an abundant number, since it is smaller than the sum of its proper divisors (36921122004).

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

21287020716 is a wasteful number, since it uses less digits than its factorization.

21287020716 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 204215 (or 204210 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 36.

Adding to 21287020716 its reverse (61702078212), we get a palindrome (82989098928).

It can be divided in two parts, 212870 and 20716, that added together give a triangular number (233586 = T₆₈₃).

The spelling of 21287020716 in words is "twenty-one billion, two hundred eighty-seven million, twenty thousand, seven hundred sixteen".