21382021 has 2 divisors, whose sum is σ = 21382022. Its totient is φ = 21382020.

The previous prime is 21382007. The next prime is 21382037. The reversal of 21382021 is 12028312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21288996 + 93025 = 4614^2 + 305^2 .

It is a cyclic number.

It is not a de Polignac number, because 21382021 - 2¹¹ = 21379973 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21382021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21382091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10691010 + 10691011.

It is an arithmetic number, because the mean of its divisors is an integer number (10691011).

Almost surely, 2^21382021 is an apocalyptic number.

It is an amenable number.

21382021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21382021 is an equidigital number, since it uses as much as digits as its factorization.

21382021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 21382021 is about 4624.0697442837. The cubic root of 21382021 is about 277.5553378264. Note that the first 3 decimals are identical.

The spelling of 21382021 in words is "twenty-one million, three hundred eighty-two thousand, twenty-one".