21361721811 has 4 divisors (see below), whose sum is σ = 28482295752. Its totient is φ = 14241147872.

The previous prime is 21361721809. The next prime is 21361721819. The reversal of 21361721811 is 11812716312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21361721811 - 2¹ = 21361721809 is a prime.

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 3 ways as a sum of consecutive naturals, for example, 3560286966 + ... + 3560286971.

It is an arithmetic number, because the mean of its divisors is an integer number (7120573938).

Almost surely, 2^21361721811 is an apocalyptic number.

21361721811 is a deficient number, since it is larger than the sum of its proper divisors (7120573941).

21361721811 is an equidigital number, since it uses as much as digits as its factorization.

21361721811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7120573940.

The product of its digits is 4032, while the sum is 33.

The spelling of 21361721811 in words is "twenty-one billion, three hundred sixty-one million, seven hundred twenty-one thousand, eight hundred eleven".