21000005451 has 12 divisors (see below), whose sum is σ = 31379318880. Its totient is φ = 13517244720.

The previous prime is 21000005449. The next prime is 21000005473. The reversal of 21000005451 is 15450000012.

21000005451 is a `hidden beast` number, since 210 + 0 + 0 + 0 + 0 + 5 + 451 = 666.

It is not a de Polignac number, because 21000005451 - 2¹ = 21000005449 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21000015451) 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 11 ways as a sum of consecutive naturals, for example, 40229635 + ... + 40230156.

It is an arithmetic number, because the mean of its divisors is an integer number (2614943240).

Almost surely, 2^21000005451 is an apocalyptic number.

21000005451 is a deficient number, since it is larger than the sum of its proper divisors (10379313429).

21000005451 is a wasteful number, since it uses less digits than its factorization.

21000005451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80459826 (or 80459823 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

Adding to 21000005451 its reverse (15450000012), we get a palindrome (36450005463).

The spelling of 21000005451 in words is "twenty-one billion, five thousand, four hundred fifty-one".