21053729 has 4 divisors (see below), whose sum is σ = 22161840. Its totient is φ = 19945620.

The previous prime is 21053713. The next prime is 21053731. The reversal of 21053729 is 92735012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21053729 - 2⁴ = 21053713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21053129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 554027 + ... + 554064.

It is an arithmetic number, because the mean of its divisors is an integer number (5540460).

Almost surely, 2^21053729 is an apocalyptic number.

It is an amenable number.

21053729 is a deficient number, since it is larger than the sum of its proper divisors (1108111).

21053729 is a wasteful number, since it uses less digits than its factorization.

21053729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1108110.

The product of its (nonzero) digits is 3780, while the sum is 29.

The square root of 21053729 is about 4588.4342645395. The cubic root of 21053729 is about 276.1275096956.

The spelling of 21053729 in words is "twenty-one million, fifty-three thousand, seven hundred twenty-nine".