21062021 has 4 divisors (see below), whose sum is σ = 21196332. Its totient is φ = 20927712.

The previous prime is 21062017. The next prime is 21062023. The reversal of 21062021 is 12026012.

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 6916900 + 14145121 = 2630^2 + 3761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21062021 - 2² = 21062017 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21061987 and 21062005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21062023) 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, 66920 + ... + 67233.

It is an arithmetic number, because the mean of its divisors is an integer number (5299083).

Almost surely, 2^21062021 is an apocalyptic number.

It is an amenable number.

21062021 is a deficient number, since it is larger than the sum of its proper divisors (134311).

21062021 is a wasteful number, since it uses less digits than its factorization.

21062021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134310.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21062021 is about 4589.3377517895. The cubic root of 21062021 is about 276.1637558285.

Adding to 21062021 its reverse (12026012), we get a palindrome (33088033).

The spelling of 21062021 in words is "twenty-one million, sixty-two thousand, twenty-one".