21415245551 has 4 divisors (see below), whose sum is σ = 24474566352. Its totient is φ = 18355924752.

The previous prime is 21415245541. The next prime is 21415245569. The reversal of 21415245551 is 15554251412.

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 21415245551 - 2¹⁸ = 21414983407 is a prime.

It is a super-2 number, since 2×21415245551² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21415245541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1529660390 + ... + 1529660403.

It is an arithmetic number, because the mean of its divisors is an integer number (6118641588).

Almost surely, 2^21415245551 is an apocalyptic number.

21415245551 is a deficient number, since it is larger than the sum of its proper divisors (3059320801).

21415245551 is an equidigital number, since it uses as much as digits as its factorization.

21415245551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3059320800.

The product of its digits is 40000, while the sum is 35.

Adding to 21415245551 its reverse (15554251412), we get a palindrome (36969496963).

The spelling of 21415245551 in words is "twenty-one billion, four hundred fifteen million, two hundred forty-five thousand, five hundred fifty-one".