21181640451 has 4 divisors (see below), whose sum is σ = 28242187272. Its totient is φ = 14121093632.

The previous prime is 21181640437. The next prime is 21181640461. The reversal of 21181640451 is 15404618112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21181640451 - 2¹⁴ = 21181624067 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21181640411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3530273406 + ... + 3530273411.

It is an arithmetic number, because the mean of its divisors is an integer number (7060546818).

Almost surely, 2^21181640451 is an apocalyptic number.

21181640451 is a deficient number, since it is larger than the sum of its proper divisors (7060546821).

21181640451 is an equidigital number, since it uses as much as digits as its factorization.

21181640451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7060546820.

The product of its (nonzero) digits is 7680, while the sum is 33.

The spelling of 21181640451 in words is "twenty-one billion, one hundred eighty-one million, six hundred forty thousand, four hundred fifty-one".