21729037 has 4 divisors (see below), whose sum is σ = 23704416. Its totient is φ = 19753660.

The previous prime is 21729031. The next prime is 21729079. The reversal of 21729037 is 73092712.

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 21729037 - 2⁷ = 21728909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21729031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 987673 + ... + 987694.

It is an arithmetic number, because the mean of its divisors is an integer number (5926104).

Almost surely, 2^21729037 is an apocalyptic number.

It is an amenable number.

21729037 is a deficient number, since it is larger than the sum of its proper divisors (1975379).

21729037 is a wasteful number, since it uses less digits than its factorization.

21729037 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1975378.

The product of its (nonzero) digits is 5292, while the sum is 31.

The square root of 21729037 is about 4661.4415152397. The cubic root of 21729037 is about 279.0488003605.

The spelling of 21729037 in words is "twenty-one million, seven hundred twenty-nine thousand, thirty-seven".