21357729 has 64 divisors (see below), whose sum is σ = 36864000. Its totient is φ = 12130560.

The previous prime is 21357719. The next prime is 21357773. The reversal of 21357729 is 92775312.

21357729 = T₁₉₀ + T₁₉₁ + ... + T₅₁₂.

It is not a de Polignac number, because 21357729 - 2⁵ = 21357697 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21357693 and 21357702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21357709) 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 63 ways as a sum of consecutive naturals, for example, 270312 + ... + 270390.

It is an arithmetic number, because the mean of its divisors is an integer number (576000).

Almost surely, 2^21357729 is an apocalyptic number.

It is an amenable number.

21357729 is a deficient number, since it is larger than the sum of its proper divisors (15506271).

21357729 is a wasteful number, since it uses less digits than its factorization.

21357729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155 (or 149 counting only the distinct ones).

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

The square root of 21357729 is about 4621.4423073322. The cubic root of 21357729 is about 277.4501882835.

The spelling of 21357729 in words is "twenty-one million, three hundred fifty-seven thousand, seven hundred twenty-nine".