21781213320 has 64 divisors (see below), whose sum is σ = 65360157120. Its totient is φ = 5806855424.

The previous prime is 21781213301. The next prime is 21781213343. The reversal of 21781213320 is 2331218712.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 504007 + ... + 545513.

It is an arithmetic number, because the mean of its divisors is an integer number (1021252455).

Almost surely, 2^21781213320 is an apocalyptic number.

21781213320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21781213320 is an abundant number, since it is smaller than the sum of its proper divisors (43578943800).

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

21781213320 is a wasteful number, since it uses less digits than its factorization.

21781213320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45894 (or 45890 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 30.

It can be divided in two parts, 217812 and 13320, that added together give a palindrome (231132).

The spelling of 21781213320 in words is "twenty-one billion, seven hundred eighty-one million, two hundred thirteen thousand, three hundred twenty".