21264451520 has 56 divisors (see below), whose sum is σ = 54531060864. Its totient is φ = 7851488256.

The previous prime is 21264451511. The next prime is 21264451529. The reversal of 21264451520 is 2515446212.

It is an interprime number because it is at equal distance from previous prime (21264451511) and next prime (21264451529).

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21264451529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2551664 + ... + 2559983.

It is an arithmetic number, because the mean of its divisors is an integer number (973768944).

Almost surely, 2^21264451520 is an apocalyptic number.

21264451520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21264451520 is an abundant number, since it is smaller than the sum of its proper divisors (33266609344).

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

21264451520 is a wasteful number, since it uses less digits than its factorization.

21264451520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5111677 (or 5111667 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 32.

Adding to 21264451520 its reverse (2515446212), we get a palindrome (23779897732).

The spelling of 21264451520 in words is "twenty-one billion, two hundred sixty-four million, four hundred fifty-one thousand, five hundred twenty".