21002261920 has 96 divisors (see below), whose sum is σ = 51318683136. Its totient is φ = 8113996800.

The previous prime is 21002261909. The next prime is 21002261923. The reversal of 21002261920 is 2916220012.

It is not an unprimeable number, because it can be changed into a prime (21002261923) 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, 2709250 + ... + 2716990.

It is an arithmetic number, because the mean of its divisors is an integer number (534569616).

Almost surely, 2^21002261920 is an apocalyptic number.

21002261920 is a gapful number since it is divisible by the number (20) 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 21002261920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25659341568).

21002261920 is an abundant number, since it is smaller than the sum of its proper divisors (30316421216).

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

21002261920 is a wasteful number, since it uses less digits than its factorization.

21002261920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8334 (or 8326 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 25.

Adding to 21002261920 its reverse (2916220012), we get a palindrome (23918481932).

The spelling of 21002261920 in words is "twenty-one billion, two million, two hundred sixty-one thousand, nine hundred twenty".