21720467 has 2 divisors, whose sum is σ = 21720468. Its totient is φ = 21720466.

The previous prime is 21720463. The next prime is 21720469. The reversal of 21720467 is 76402712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21720467 - 2² = 21720463 is a prime.

Together with 21720469, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21720463) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10860233 + 10860234.

It is an arithmetic number, because the mean of its divisors is an integer number (10860234).

Almost surely, 2^21720467 is an apocalyptic number.

21720467 is a deficient number, since it is larger than the sum of its proper divisors (1).

21720467 is an equidigital number, since it uses as much as digits as its factorization.

21720467 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4704, while the sum is 29.

The square root of 21720467 is about 4660.5221810437. The cubic root of 21720467 is about 279.0121096306.

The spelling of 21720467 in words is "twenty-one million, seven hundred twenty thousand, four hundred sixty-seven".