21801929 has 2 divisors, whose sum is σ = 21801930. Its totient is φ = 21801928.

The previous prime is 21801893. The next prime is 21801931. The reversal of 21801929 is 92910812.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21603904 + 198025 = 4648^2 + 445^2 .

It is a cyclic number.

It is not a de Polignac number, because 21801929 - 2⁸ = 21801673 is a prime.

Together with 21801931, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21801895 and 21801904.

It is not a weakly prime, because it can be changed into another prime (21806929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10900964 + 10900965.

It is an arithmetic number, because the mean of its divisors is an integer number (10900965).

Almost surely, 2^21801929 is an apocalyptic number.

It is an amenable number.

21801929 is a deficient number, since it is larger than the sum of its proper divisors (1).

21801929 is an equidigital number, since it uses as much as digits as its factorization.

21801929 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 21801929 is about 4669.2535806058. The cubic root of 21801929 is about 279.3604834915.

The spelling of 21801929 in words is "twenty-one million, eight hundred one thousand, nine hundred twenty-nine".