21020747 has 4 divisors (see below), whose sum is σ = 22931736. Its totient is φ = 19109760.

The previous prime is 21020719. The next prime is 21020749. The reversal of 21020747 is 74702012.

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

It is a cyclic number.

It is not a de Polignac number, because 21020747 - 2⁶ = 21020683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21020749) 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, 955478 + ... + 955499.

It is an arithmetic number, because the mean of its divisors is an integer number (5732934).

Almost surely, 2^21020747 is an apocalyptic number.

21020747 is a deficient number, since it is larger than the sum of its proper divisors (1910989).

21020747 is a wasteful number, since it uses less digits than its factorization.

21020747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1910988.

The product of its (nonzero) digits is 784, while the sum is 23.

The square root of 21020747 is about 4584.8388194134. The cubic root of 21020747 is about 275.9832439243.

Adding to 21020747 its reverse (74702012), we get a palindrome (95722759).

The spelling of 21020747 in words is "twenty-one million, twenty thousand, seven hundred forty-seven".