21020737 has 4 divisors (see below), whose sum is σ = 21745620. Its totient is φ = 20295856.

The previous prime is 21020719. The next prime is 21020749. The reversal of 21020737 is 73702012.

21020737 is nontrivially palindromic in base 16.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13535041 + 7485696 = 3679^2 + 2736^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020737 - 2¹⁵ = 20987969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21020777) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 362398 + ... + 362455.

It is an arithmetic number, because the mean of its divisors is an integer number (5436405).

Almost surely, 2^21020737 is an apocalyptic number.

It is an amenable number.

21020737 is a deficient number, since it is larger than the sum of its proper divisors (724883).

21020737 is an equidigital number, since it uses as much as digits as its factorization.

21020737 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724882.

The product of its (nonzero) digits is 588, while the sum is 22.

The square root of 21020737 is about 4584.8377288624. The cubic root of 21020737 is about 275.9832001607.

Adding to 21020737 its reverse (73702012), we get a palindrome (94722749).

The spelling of 21020737 in words is "twenty-one million, twenty thousand, seven hundred thirty-seven".