21263729 has 2 divisors, whose sum is σ = 21263730. Its totient is φ = 21263728.

The previous prime is 21263713. The next prime is 21263731. The reversal of 21263729 is 92736212.

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., 11404129 + 9859600 = 3377^2 + 3140^2 .

It is a cyclic number.

It is not a de Polignac number, because 21263729 - 2⁴ = 21263713 is a prime.

Together with 21263731, 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 = 21263695 and 21263704.

It is not a weakly prime, because it can be changed into another prime (21263779) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10631864 + 10631865.

It is an arithmetic number, because the mean of its divisors is an integer number (10631865).

Almost surely, 2^21263729 is an apocalyptic number.

It is an amenable number.

21263729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21263729 is an equidigital number, since it uses as much as digits as its factorization.

21263729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 32.

The square root of 21263729 is about 4611.2611073328. The cubic root of 21263729 is about 277.0425501674.

The spelling of 21263729 in words is "twenty-one million, two hundred sixty-three thousand, seven hundred twenty-nine".