21210145521 has 16 divisors (see below), whose sum is σ = 28329148800. Its totient is φ = 14115644928.

The previous prime is 21210145487. The next prime is 21210145577. The reversal of 21210145521 is 12554101212.

It is a happy number.

It is not a de Polignac number, because 21210145521 - 2⁶ = 21210145457 is a prime.

It is a super-2 number, since 2×21210145521² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21210145491 and 21210145500.

It is not an unprimeable number, because it can be changed into a prime (21210155521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6691425 + ... + 6694593.

It is an arithmetic number, because the mean of its divisors is an integer number (1770571800).

Almost surely, 2^21210145521 is an apocalyptic number.

It is an amenable number.

21210145521 is a deficient number, since it is larger than the sum of its proper divisors (7119003279).

21210145521 is a wasteful number, since it uses less digits than its factorization.

21210145521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6328.

The product of its (nonzero) digits is 800, while the sum is 24.

Adding to 21210145521 its reverse (12554101212), we get a palindrome (33764246733).

The spelling of 21210145521 in words is "twenty-one billion, two hundred ten million, one hundred forty-five thousand, five hundred twenty-one".