21146921 has 2 divisors, whose sum is σ = 21146922. Its totient is φ = 21146920.

The previous prime is 21146911. The next prime is 21146953. The reversal of 21146921 is 12964112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19456921 + 1690000 = 4411^2 + 1300^2 .

It is a cyclic number.

It is not a de Polignac number, because 21146921 - 2¹⁸ = 20884777 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21146911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10573460 + 10573461.

It is an arithmetic number, because the mean of its divisors is an integer number (10573461).

Almost surely, 2^21146921 is an apocalyptic number.

It is an amenable number.

21146921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21146921 is an equidigital number, since it uses as much as digits as its factorization.

21146921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 26.

The square root of 21146921 is about 4598.5781498198. The cubic root of 21146921 is about 276.5343259903.

The spelling of 21146921 in words is "twenty-one million, one hundred forty-six thousand, nine hundred twenty-one".