21929849 has 2 divisors, whose sum is σ = 21929850. Its totient is φ = 21929848.

The previous prime is 21929821. The next prime is 21929851. The reversal of 21929849 is 94892912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17909824 + 4020025 = 4232^2 + 2005^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21929849 is a prime.

Together with 21929851, 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 (21929549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10964924 + 10964925.

It is an arithmetic number, because the mean of its divisors is an integer number (10964925).

Almost surely, 2^21929849 is an apocalyptic number.

It is an amenable number.

21929849 is a deficient number, since it is larger than the sum of its proper divisors (1).

21929849 is an equidigital number, since it uses as much as digits as its factorization.

21929849 is an evil number, because the sum of its binary digits is even.

The product of its digits is 93312, while the sum is 44.

The square root of 21929849 is about 4682.9316672358. The cubic root of 21929849 is about 279.9057888827.

The spelling of 21929849 in words is "twenty-one million, nine hundred twenty-nine thousand, eight hundred forty-nine".