21215220642520 has 16 divisors (see below), whose sum is σ = 47734246445760. Its totient is φ = 8486088256992.

The previous prime is 21215220642439. The next prime is 21215220642547. The reversal of 21215220642520 is 2524602251212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 265190257992 + ... + 265190258071.

It is an arithmetic number, because the mean of its divisors is an integer number (2983390402860).

Almost surely, 2^{21215220642520} is an apocalyptic number.

21215220642520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21215220642520 is an abundant number, since it is smaller than the sum of its proper divisors (26519025803240).

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

21215220642520 is a wasteful number, since it uses less digits than its factorization.

21215220642520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 530380516074 (or 530380516070 counting only the distinct ones).

The product of its (nonzero) digits is 38400, while the sum is 34.

Adding to 21215220642520 its reverse (2524602251212), we get a palindrome (23739822893732).

The spelling of 21215220642520 in words is "twenty-one trillion, two hundred fifteen billion, two hundred twenty million, six hundred forty-two thousand, five hundred twenty".