21440254551 has 4 divisors (see below), whose sum is σ = 28587006072. Its totient is φ = 14293503032.

The previous prime is 21440254523. The next prime is 21440254559. The reversal of 21440254551 is 15545204412.

It is a happy number.

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 21440254551 - 2¹¹ = 21440252503 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21440254559) 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, 3573375756 + ... + 3573375761.

It is an arithmetic number, because the mean of its divisors is an integer number (7146751518).

Almost surely, 2^21440254551 is an apocalyptic number.

21440254551 is a deficient number, since it is larger than the sum of its proper divisors (7146751521).

21440254551 is an equidigital number, since it uses as much as digits as its factorization.

21440254551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7146751520.

The product of its (nonzero) digits is 32000, while the sum is 33.

Adding to 21440254551 its reverse (15545204412), we get a palindrome (36985458963).

The spelling of 21440254551 in words is "twenty-one billion, four hundred forty million, two hundred fifty-four thousand, five hundred fifty-one".