21001224564 has 48 divisors (see below), whose sum is σ = 54459216000. Its totient is φ = 6998917248.

The previous prime is 21001224547. The next prime is 21001224577. The reversal of 21001224564 is 46542210012.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 565084 + ... + 601100.

It is an arithmetic number, because the mean of its divisors is an integer number (1134567000).

Almost surely, 2^21001224564 is an apocalyptic number.

It is an amenable number.

21001224564 is an abundant number, since it is smaller than the sum of its proper divisors (33457991436).

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

21001224564 is a wasteful number, since it uses less digits than its factorization.

21001224564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41429 (or 41421 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

Adding to 21001224564 its reverse (46542210012), we get a palindrome (67543434576).

The spelling of 21001224564 in words is "twenty-one billion, one million, two hundred twenty-four thousand, five hundred sixty-four".