21261211620 has 96 divisors (see below), whose sum is σ = 65005065216. Its totient is φ = 5149334400.

The previous prime is 21261211607. The next prime is 21261211681. The reversal of 21261211620 is 2611216212.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 705297 + ... + 734823.

It is an arithmetic number, because the mean of its divisors is an integer number (677136096).

Almost surely, 2^21261211620 is an apocalyptic number.

21261211620 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 21261211620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32502532608).

21261211620 is an abundant number, since it is smaller than the sum of its proper divisors (43743853596).

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

21261211620 is a wasteful number, since it uses less digits than its factorization.

21261211620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30641 (or 30639 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 24.

Adding to 21261211620 its reverse (2611216212), we get a palindrome (23872427832).

The spelling of 21261211620 in words is "twenty-one billion, two hundred sixty-one million, two hundred eleven thousand, six hundred twenty".