21052731 has 8 divisors (see below), whose sum is σ = 32080384. Its totient is φ = 12030120.

The previous prime is 21052729. The next prime is 21052739. The reversal of 21052731 is 13725012.

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

It is not a de Polignac number, because 21052731 - 2¹ = 21052729 is a prime.

It is a super-2 number, since 2×21052731² = 886434965116722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 1002511 = 21052731 / (2 + 1 + 0 + 5 + 2 + 7 + 3 + 1).

It is a junction number, because it is equal to n+sod(n) for n = 21052698 and 21052707.

It is not an unprimeable number, because it can be changed into a prime (21052739) 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, 501235 + ... + 501276.

It is an arithmetic number, because the mean of its divisors is an integer number (4010048).

Almost surely, 2^21052731 is an apocalyptic number.

21052731 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21052731 is a deficient number, since it is larger than the sum of its proper divisors (11027653).

21052731 is a wasteful number, since it uses less digits than its factorization.

21052731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1002521.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21052731 is about 4588.3255115565. The cubic root of 21052731 is about 276.1231465792.

Adding to 21052731 its reverse (13725012), we get a palindrome (34777743).

The spelling of 21052731 in words is "twenty-one million, fifty-two thousand, seven hundred thirty-one".