21312495551 has 2 divisors, whose sum is σ = 21312495552. Its totient is φ = 21312495550.

The previous prime is 21312495527. The next prime is 21312495563. The reversal of 21312495551 is 15559421312.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21312495551 - 2²² = 21308301247 is a prime.

It is a super-2 number, since 2×21312495551² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21312495511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656247775 + 10656247776.

It is an arithmetic number, because the mean of its divisors is an integer number (10656247776).

Almost surely, 2^21312495551 is an apocalyptic number.

21312495551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312495551 is an equidigital number, since it uses as much as digits as its factorization.

21312495551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 54000, while the sum is 38.

The spelling of 21312495551 in words is "twenty-one billion, three hundred twelve million, four hundred ninety-five thousand, five hundred fifty-one".