21365731 has 8 divisors (see below), whose sum is σ = 21837600. Its totient is φ = 20896512.

The previous prime is 21365723. The next prime is 21365737. The reversal of 21365731 is 13756312.

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 21365731 - 2³ = 21365723 is a prime.

It is a super-2 number, since 2×21365731² = 912988922328722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21365731.

It is not an unprimeable number, because it can be changed into a prime (21365737) 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 7 ways as a sum of consecutive naturals, for example, 31411 + ... + 32083.

It is an arithmetic number, because the mean of its divisors is an integer number (2729700).

Almost surely, 2^21365731 is an apocalyptic number.

21365731 is a deficient number, since it is larger than the sum of its proper divisors (471869).

21365731 is an equidigital number, since it uses as much as digits as its factorization.

21365731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1325.

The product of its digits is 3780, while the sum is 28.

The square root of 21365731 is about 4622.3079732965. The cubic root of 21365731 is about 277.4848342766.

The spelling of 21365731 in words is "twenty-one million, three hundred sixty-five thousand, seven hundred thirty-one".