21711021 has 4 divisors (see below), whose sum is σ = 28948032. Its totient is φ = 14474012.

The previous prime is 21710993. The next prime is 21711037. The reversal of 21711021 is 12011712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21711021 - 2⁶ = 21710957 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21711071) 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, 3618501 + ... + 3618506.

It is an arithmetic number, because the mean of its divisors is an integer number (7237008).

Almost surely, 2^21711021 is an apocalyptic number.

It is an amenable number.

21711021 is a deficient number, since it is larger than the sum of its proper divisors (7237011).

21711021 is an equidigital number, since it uses as much as digits as its factorization.

21711021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7237010.

The product of its (nonzero) digits is 28, while the sum is 15.

The square root of 21711021 is about 4659.5086650848. The cubic root of 21711021 is about 278.9716572999.

Adding to 21711021 its reverse (12011712), we get a palindrome (33722733).

The spelling of 21711021 in words is "twenty-one million, seven hundred eleven thousand, twenty-one".