21011013521 has 8 divisors (see below), whose sum is σ = 21937807104. Its totient is φ = 20085325920.

The previous prime is 21011013431. The next prime is 21011013553. The reversal of 21011013521 is 12531011012.

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

It is not a de Polignac number, because 21011013521 - 2²² = 21006819217 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21011013521.

It is not an unprimeable number, because it can be changed into a prime (21011013581) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 237545 + ... + 313766.

It is an arithmetic number, because the mean of its divisors is an integer number (2742225888).

Almost surely, 2^21011013521 is an apocalyptic number.

It is an amenable number.

21011013521 is a deficient number, since it is larger than the sum of its proper divisors (926793583).

21011013521 is a wasteful number, since it uses less digits than its factorization.

21011013521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 552991.

The product of its (nonzero) digits is 60, while the sum is 17.

Adding to 21011013521 its reverse (12531011012), we get a palindrome (33542024533).

The spelling of 21011013521 in words is "twenty-one billion, eleven million, thirteen thousand, five hundred twenty-one".