21500204451 has 32 divisors (see below), whose sum is σ = 31738728960. Its totient is φ = 12836678400.

The previous prime is 21500204449. The next prime is 21500204461. The reversal of 21500204451 is 15440200512.

It is not a de Polignac number, because 21500204451 - 2¹ = 21500204449 is a prime.

It is a super-2 number, since 2×21500204451² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21500204461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3776415 + ... + 3782103.

It is an arithmetic number, because the mean of its divisors is an integer number (991835280).

Almost surely, 2^21500204451 is an apocalyptic number.

21500204451 is a deficient number, since it is larger than the sum of its proper divisors (10238524509).

21500204451 is a wasteful number, since it uses less digits than its factorization.

21500204451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7387.

The product of its (nonzero) digits is 1600, while the sum is 24.

Adding to 21500204451 its reverse (15440200512), we get a palindrome (36940404963).

The spelling of 21500204451 in words is "twenty-one billion, five hundred million, two hundred four thousand, four hundred fifty-one".