21012521034540 has 192 divisors, whose sum is σ = 67884729163776. Its totient is φ = 4756876873728.

The previous prime is 21012521034493. The next prime is 21012521034553. The reversal of 21012521034540 is 4543012521012.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21012521034498 and 21012521034507.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 65001349 + ... + 65323811.

It is an arithmetic number, because the mean of its divisors is an integer number (353566297728).

Almost surely, 2^{21012521034540} is an apocalyptic number.

21012521034540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21012521034540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33942364581888).

21012521034540 is an abundant number, since it is smaller than the sum of its proper divisors (46872208129236).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21012521034540 is a wasteful number, since it uses less digits than its factorization.

21012521034540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 323968 (or 323966 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 30.

Adding to 21012521034540 its reverse (4543012521012), we get a palindrome (25555533555552).

The spelling of 21012521034540 in words is "twenty-one trillion, twelve billion, five hundred twenty-one million, thirty-four thousand, five hundred forty".