21657236551 has 2 divisors, whose sum is σ = 21657236552. Its totient is φ = 21657236550.

The previous prime is 21657236539. The next prime is 21657236617. The reversal of 21657236551 is 15563275612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21657236551 - 2⁹ = 21657236039 is a prime.

It is a super-4 number, since 4×21657236551⁴ (a number of 42 digits) contains 4444 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21657236498 and 21657236507.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21657236351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10828618275 + 10828618276.

It is an arithmetic number, because the mean of its divisors is an integer number (10828618276).

Almost surely, 2^21657236551 is an apocalyptic number.

21657236551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21657236551 is an equidigital number, since it uses as much as digits as its factorization.

21657236551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 378000, while the sum is 43.

The spelling of 21657236551 in words is "twenty-one billion, six hundred fifty-seven million, two hundred thirty-six thousand, five hundred fifty-one".