221010021 has 6 divisors (see below), whose sum is σ = 319236710. Its totient is φ = 147340008.

The previous prime is 221010011. The next prime is 221010037. The reversal of 221010021 is 120010122.

It can be written as a sum of positive squares in only one way, i.e., 137945025 + 83064996 = 11745^2 + 9114^2 .

It is not a de Polignac number, because 221010021 - 2²² = 216815717 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 24556669 = 221010021 / (2 + 2 + 1 + 0 + 1 + 0 + 0 + 2 + 1).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221009985 and 221010012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221010001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 12278326 + ... + 12278343.

Almost surely, 2^221010021 is an apocalyptic number.

It is an amenable number.

221010021 is a deficient number, since it is larger than the sum of its proper divisors (98226689).

221010021 is a wasteful number, since it uses less digits than its factorization.

221010021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24556675 (or 24556672 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 221010021 is about 14866.4057862013. The cubic root of 221010021 is about 604.6034976835.

Adding to 221010021 its reverse (120010122), we get a palindrome (341020143).

The spelling of 221010021 in words is "two hundred twenty-one million, ten thousand, twenty-one".