21573779 has 2 divisors, whose sum is σ = 21573780. Its totient is φ = 21573778.

The previous prime is 21573757. The next prime is 21573781. The reversal of 21573779 is 97737512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21573779 is a prime.

Together with 21573781, 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 (21573719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10786889 + 10786890.

It is an arithmetic number, because the mean of its divisors is an integer number (10786890).

Almost surely, 2^21573779 is an apocalyptic number.

21573779 is a deficient number, since it is larger than the sum of its proper divisors (1).

21573779 is an equidigital number, since it uses as much as digits as its factorization.

21573779 is an evil number, because the sum of its binary digits is even.

The product of its digits is 92610, while the sum is 41.

The square root of 21573779 is about 4644.7582283688. The cubic root of 21573779 is about 278.3825926258.

The spelling of 21573779 in words is "twenty-one million, five hundred seventy-three thousand, seven hundred seventy-nine".