21554434551 has 32 divisors (see below), whose sum is σ = 31082913792. Its totient is φ = 13207420800.

The previous prime is 21554434547. The next prime is 21554434591. The reversal of 21554434551 is 15543445512.

It is not a de Polignac number, because 21554434551 - 2² = 21554434547 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21554434501) 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 31 ways as a sum of consecutive naturals, for example, 15698101 + ... + 15699473.

It is an arithmetic number, because the mean of its divisors is an integer number (971341056).

Almost surely, 2^21554434551 is an apocalyptic number.

21554434551 is a deficient number, since it is larger than the sum of its proper divisors (9528479241).

21554434551 is a wasteful number, since it uses less digits than its factorization.

21554434551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2823.

The product of its digits is 240000, while the sum is 39.

The spelling of 21554434551 in words is "twenty-one billion, five hundred fifty-four million, four hundred thirty-four thousand, five hundred fifty-one".