21210355451 has 4 divisors (see below), whose sum is σ = 21257595000. Its totient is φ = 21163115904.

The previous prime is 21210355429. The next prime is 21210355457. The reversal of 21210355451 is 15455301212.

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 21210355451 - 2¹⁰ = 21210354427 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21210355457) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23619101 + ... + 23619998.

It is an arithmetic number, because the mean of its divisors is an integer number (5314398750).

Almost surely, 2^21210355451 is an apocalyptic number.

21210355451 is a deficient number, since it is larger than the sum of its proper divisors (47239549).

21210355451 is an equidigital number, since it uses as much as digits as its factorization.

21210355451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47239548.

The product of its (nonzero) digits is 6000, while the sum is 29.

Adding to 21210355451 its reverse (15455301212), we get a palindrome (36665656663).

The spelling of 21210355451 in words is "twenty-one billion, two hundred ten million, three hundred fifty-five thousand, four hundred fifty-one".