21042051551 has 2 divisors, whose sum is σ = 21042051552. Its totient is φ = 21042051550.

The previous prime is 21042051539. The next prime is 21042051577. The reversal of 21042051551 is 15515024012.

It is an a-pointer prime, because the next prime (21042051577) can be obtained adding 21042051551 to its sum of digits (26).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21042051551 - 2²⁶ = 20974942687 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21042051551.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21042051451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521025775 + 10521025776.

It is an arithmetic number, because the mean of its divisors is an integer number (10521025776).

Almost surely, 2^21042051551 is an apocalyptic number.

21042051551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21042051551 is an equidigital number, since it uses as much as digits as its factorization.

21042051551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2000, while the sum is 26.

Adding to 21042051551 its reverse (15515024012), we get a palindrome (36557075563).

The spelling of 21042051551 in words is "twenty-one billion, forty-two million, fifty-one thousand, five hundred fifty-one".