21029221 has 4 divisors (see below), whose sum is σ = 22266252. Its totient is φ = 19792192.

The previous prime is 21029207. The next prime is 21029237. The reversal of 21029221 is 12292012.

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 15124321 + 5904900 = 3889^2 + 2430^2 .

It is a cyclic number.

It is not a de Polignac number, because 21029221 - 2⁵ = 21029189 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21024221) 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, 618490 + ... + 618523.

It is an arithmetic number, because the mean of its divisors is an integer number (5566563).

Almost surely, 2^21029221 is an apocalyptic number.

It is an amenable number.

21029221 is a deficient number, since it is larger than the sum of its proper divisors (1237031).

21029221 is a wasteful number, since it uses less digits than its factorization.

21029221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1237030.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 21029221 is about 4585.7628591108. The cubic root of 21029221 is about 276.0203242402.

The spelling of 21029221 in words is "twenty-one million, twenty-nine thousand, two hundred twenty-one".