21003731 has 8 divisors (see below), whose sum is σ = 24294144. Its totient is φ = 17785800.

The previous prime is 21003727. The next prime is 21003751. The reversal of 21003731 is 13730012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21003731 - 2² = 21003727 is a prime.

It is a super-2 number, since 2×21003731² = 882313431840722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21003751) 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 7 ways as a sum of consecutive naturals, for example, 17495 + ... + 18656.

It is an arithmetic number, because the mean of its divisors is an integer number (3036768).

Almost surely, 2^21003731 is an apocalyptic number.

21003731 is a deficient number, since it is larger than the sum of its proper divisors (3290413).

21003731 is an equidigital number, since it uses as much as digits as its factorization.

21003731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36241.

The product of its (nonzero) digits is 126, while the sum is 17.

The square root of 21003731 is about 4582.9827623503. The cubic root of 21003731 is about 275.9087556326.

Adding to 21003731 its reverse (13730012), we get a palindrome (34733743).

The spelling of 21003731 in words is "twenty-one million, three thousand, seven hundred thirty-one".