21929389 has 2 divisors, whose sum is σ = 21929390. Its totient is φ = 21929388.

The previous prime is 21929377. The next prime is 21929393. The reversal of 21929389 is 98392912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19096900 + 2832489 = 4370^2 + 1683^2 .

It is a cyclic number.

It is not a de Polignac number, because 21929389 - 2⁵ = 21929357 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21929339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10964694 + 10964695.

It is an arithmetic number, because the mean of its divisors is an integer number (10964695).

Almost surely, 2^21929389 is an apocalyptic number.

It is an amenable number.

21929389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21929389 is an equidigital number, since it uses as much as digits as its factorization.

21929389 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 43.

The square root of 21929389 is about 4682.8825524457. The cubic root of 21929389 is about 279.9038317700.

The spelling of 21929389 in words is "twenty-one million, nine hundred twenty-nine thousand, three hundred eighty-nine".