21569730921 has 8 divisors (see below), whose sum is σ = 31955156960. Its totient is φ = 14379820596.

The previous prime is 21569730899. The next prime is 21569730953. The reversal of 21569730921 is 12903796512.

It is a happy number.

It is not a de Polignac number, because 21569730921 - 2¹³ = 21569722729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21569730971) 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 7 ways as a sum of consecutive naturals, for example, 399439435 + ... + 399439488.

It is an arithmetic number, because the mean of its divisors is an integer number (3994394620).

Almost surely, 2^21569730921 is an apocalyptic number.

It is an amenable number.

21569730921 is a deficient number, since it is larger than the sum of its proper divisors (10385426039).

21569730921 is an equidigital number, since it uses as much as digits as its factorization.

21569730921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 798878932 (or 798878926 counting only the distinct ones).

The product of its (nonzero) digits is 204120, while the sum is 45.

The spelling of 21569730921 in words is "twenty-one billion, five hundred sixty-nine million, seven hundred thirty thousand, nine hundred twenty-one".