21500007221 has 8 divisors (see below), whose sum is σ = 26805203904. Its totient is φ = 16753252320.

The previous prime is 21500007203. The next prime is 21500007241. The reversal of 21500007221 is 12270000512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21500007221 - 2³⁴ = 4320138037 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21500007193 and 21500007202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21500007241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 139610360 + ... + 139610513.

It is an arithmetic number, because the mean of its divisors is an integer number (3350650488).

Almost surely, 2^21500007221 is an apocalyptic number.

It is an amenable number.

21500007221 is a deficient number, since it is larger than the sum of its proper divisors (5305196683).

21500007221 is a wasteful number, since it uses less digits than its factorization.

21500007221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 279220891.

The product of its (nonzero) digits is 280, while the sum is 20.

Adding to 21500007221 its reverse (12270000512), we get a palindrome (33770007733).

The spelling of 21500007221 in words is "twenty-one billion, five hundred million, seven thousand, two hundred twenty-one".