21940729 has 2 divisors, whose sum is σ = 21940730. Its totient is φ = 21940728.

The previous prime is 21940703. The next prime is 21940757. The reversal of 21940729 is 92704912.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18079504 + 3861225 = 4252^2 + 1965^2 .

It is a cyclic number.

It is not a de Polignac number, because 21940729 - 2⁷ = 21940601 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21940694 and 21940703.

It is not a weakly prime, because it can be changed into another prime (21940759) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10970364 + 10970365.

It is an arithmetic number, because the mean of its divisors is an integer number (10970365).

Almost surely, 2^21940729 is an apocalyptic number.

It is an amenable number.

21940729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21940729 is an equidigital number, since it uses as much as digits as its factorization.

21940729 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 34.

The square root of 21940729 is about 4684.0931886546. The cubic root of 21940729 is about 279.9520708778.

The spelling of 21940729 in words is "twenty-one million, nine hundred forty thousand, seven hundred twenty-nine".