21020771 has 4 divisors (see below), whose sum is σ = 21162000. Its totient is φ = 20879544.

The previous prime is 21020761. The next prime is 21020777. The reversal of 21020771 is 17702012.

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 21020771 - 2¹⁴ = 21004387 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, 70391 + ... + 70688.

It is an arithmetic number, because the mean of its divisors is an integer number (5290500).

Almost surely, 2^21020771 is an apocalyptic number.

21020771 is a deficient number, since it is larger than the sum of its proper divisors (141229).

21020771 is a wasteful number, since it uses less digits than its factorization.

21020771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141228.

The product of its (nonzero) digits is 196, while the sum is 20.

The square root of 21020771 is about 4584.8414367348. The cubic root of 21020771 is about 275.9833489570.

Adding to 21020771 its reverse (17702012), we get a palindrome (38722783).

The spelling of 21020771 in words is "twenty-one million, twenty thousand, seven hundred seventy-one".