21720910111 has 4 divisors (see below), whose sum is σ = 21729745800. Its totient is φ = 21712074424.

The previous prime is 21720910109. The next prime is 21720910147. The reversal of 21720910111 is 11101902712.

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 21720910111 - 2¹ = 21720910109 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720910411) 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, 4414156 + ... + 4419073.

It is an arithmetic number, because the mean of its divisors is an integer number (5432436450).

Almost surely, 2^21720910111 is an apocalyptic number.

21720910111 is a deficient number, since it is larger than the sum of its proper divisors (8835689).

21720910111 is an equidigital number, since it uses as much as digits as its factorization.

21720910111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8835688.

The product of its (nonzero) digits is 252, while the sum is 25.

The spelling of 21720910111 in words is "twenty-one billion, seven hundred twenty million, nine hundred ten thousand, one hundred eleven".