21720927 has 4 divisors (see below), whose sum is σ = 28961240. Its totient is φ = 14480616.

The previous prime is 21720911. The next prime is 21720929. The reversal of 21720927 is 72902712.

It is a happy number.

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

It is not a de Polignac number, because 21720927 - 2⁴ = 21720911 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21720894 and 21720903.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3620152 + ... + 3620157.

It is an arithmetic number, because the mean of its divisors is an integer number (7240310).

Almost surely, 2^21720927 is an apocalyptic number.

21720927 is a deficient number, since it is larger than the sum of its proper divisors (7240313).

21720927 is an equidigital number, since it uses as much as digits as its factorization.

21720927 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7240312.

The product of its (nonzero) digits is 3528, while the sum is 30.

The square root of 21720927 is about 4660.5715314755. The cubic root of 21720927 is about 279.0140792731.

The spelling of 21720927 in words is "twenty-one million, seven hundred twenty thousand, nine hundred twenty-seven".