21534400243 has 2 divisors, whose sum is σ = 21534400244. Its totient is φ = 21534400242.

The previous prime is 21534400231. The next prime is 21534400249. The reversal of 21534400243 is 34200443512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21534400243 - 2¹⁷ = 21534269171 is a prime.

It is not a weakly prime, because it can be changed into another prime (21534400249) 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 as a sum of consecutive naturals, namely, 10767200121 + 10767200122.

It is an arithmetic number, because the mean of its divisors is an integer number (10767200122).

Almost surely, 2^21534400243 is an apocalyptic number.

21534400243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21534400243 is an equidigital number, since it uses as much as digits as its factorization.

21534400243 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11520, while the sum is 28.

Adding to 21534400243 its reverse (34200443512), we get a palindrome (55734843755).

The spelling of 21534400243 in words is "twenty-one billion, five hundred thirty-four million, four hundred thousand, two hundred forty-three".