21020711 has 4 divisors (see below), whose sum is σ = 21142392. Its totient is φ = 20899032.

The previous prime is 21020683. The next prime is 21020719. The reversal of 21020711 is 11702012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020711 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020719) 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, 60581 + ... + 60926.

It is an arithmetic number, because the mean of its divisors is an integer number (5285598).

Almost surely, 2^21020711 is an apocalyptic number.

21020711 is a deficient number, since it is larger than the sum of its proper divisors (121681).

21020711 is a wasteful number, since it uses less digits than its factorization.

21020711 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121680.

The product of its (nonzero) digits is 28, while the sum is 14.

The square root of 21020711 is about 4584.8348934286. The cubic root of 21020711 is about 275.9830863751.

Adding to 21020711 its reverse (11702012), we get a palindrome (32722723).

The spelling of 21020711 in words is "twenty-one million, twenty thousand, seven hundred eleven".