21729357 has 32 divisors (see below), whose sum is σ = 35804160. Its totient is φ = 12934080.

The previous prime is 21729341. The next prime is 21729361. The reversal of 21729357 is 75392712.

It is not a de Polignac number, because 21729357 - 2⁴ = 21729341 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21729307) 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 in 31 ways as a sum of consecutive naturals, for example, 9883 + ... + 11879.

It is an arithmetic number, because the mean of its divisors is an integer number (1118880).

Almost surely, 2^21729357 is an apocalyptic number.

21729357 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21729357 is a deficient number, since it is larger than the sum of its proper divisors (14074803).

21729357 is a wasteful number, since it uses less digits than its factorization.

21729357 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2050 (or 2044 counting only the distinct ones).

The product of its digits is 26460, while the sum is 36.

The square root of 21729357 is about 4661.4758392595. The cubic root of 21729357 is about 279.0501701893.

The spelling of 21729357 in words is "twenty-one million, seven hundred twenty-nine thousand, three hundred fifty-seven".