21513444454 has 4 divisors (see below), whose sum is σ = 32270166684. Its totient is φ = 10756722226.

The previous prime is 21513444451. The next prime is 21513444457. The reversal of 21513444454 is 45444431512.

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

It is an interprime number because it is at equal distance from previous prime (21513444451) and next prime (21513444457).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513444451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5378361112 + ... + 5378361115.

It is an arithmetic number, because the mean of its divisors is an integer number (8067541671).

Almost surely, 2^21513444454 is an apocalyptic number.

21513444454 is a deficient number, since it is larger than the sum of its proper divisors (10756722230).

21513444454 is a wasteful number, since it uses less digits than its factorization.

21513444454 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10756722229.

The product of its digits is 153600, while the sum is 37.

Adding to 21513444454 its reverse (45444431512), we get a palindrome (66957875966).

The spelling of 21513444454 in words is "twenty-one billion, five hundred thirteen million, four hundred forty-four thousand, four hundred fifty-four".