21535540221 has 16 divisors (see below), whose sum is σ = 30929665536. Its totient is φ = 13249709376.

The previous prime is 21535540207. The next prime is 21535540237. The reversal of 21535540221 is 12204553512.

It is not a de Polignac number, because 21535540221 - 2¹⁰ = 21535539197 is a prime.

It is a super-2 number, since 2×21535540221² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21535541221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 124711 + ... + 242123.

It is an arithmetic number, because the mean of its divisors is an integer number (1933104096).

Almost surely, 2^21535540221 is an apocalyptic number.

It is an amenable number.

21535540221 is a deficient number, since it is larger than the sum of its proper divisors (9394125315).

21535540221 is a wasteful number, since it uses less digits than its factorization.

21535540221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 122132.

The product of its (nonzero) digits is 12000, while the sum is 30.

The spelling of 21535540221 in words is "twenty-one billion, five hundred thirty-five million, five hundred forty thousand, two hundred twenty-one".