21361721810 has 32 divisors (see below), whose sum is σ = 45173322432. Its totient is φ = 7170367680.

The previous prime is 21361721809. The next prime is 21361721819. The reversal of 21361721810 is 1812716312.

It is a super-2 number, since 2×21361721810² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21361721819) 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, 7467704 + ... + 7470563.

It is an arithmetic number, because the mean of its divisors is an integer number (1411666326).

Almost surely, 2^21361721810 is an apocalyptic number.

21361721810 is an abundant number, since it is smaller than the sum of its proper divisors (23811600622).

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

21361721810 is a wasteful number, since it uses less digits than its factorization.

21361721810 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14938298.

The product of its (nonzero) digits is 4032, while the sum is 32.

The spelling of 21361721810 in words is "twenty-one billion, three hundred sixty-one million, seven hundred twenty-one thousand, eight hundred ten".