21849979 has 2 divisors, whose sum is σ = 21849980. Its totient is φ = 21849978.

The previous prime is 21849941. The next prime is 21850027. The reversal of 21849979 is 97994812.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21849979 is a prime.

It is not a weakly prime, because it can be changed into another prime (21843979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10924989 + 10924990.

It is an arithmetic number, because the mean of its divisors is an integer number (10924990).

Almost surely, 2^21849979 is an apocalyptic number.

21849979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21849979 is an equidigital number, since it uses as much as digits as its factorization.

21849979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 326592, while the sum is 49.

The square root of 21849979 is about 4674.3961107292. The cubic root of 21849979 is about 279.5655635398.

The spelling of 21849979 in words is "twenty-one million, eight hundred forty-nine thousand, nine hundred seventy-nine".