21533420749 has 2 divisors, whose sum is σ = 21533420750. Its totient is φ = 21533420748.

The previous prime is 21533420731. The next prime is 21533420773. The reversal of 21533420749 is 94702433512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19834497225 + 1698923524 = 140835^2 + 41218^2 .

It is a cyclic number.

It is not a de Polignac number, because 21533420749 - 2²³ = 21525032141 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21533420729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10766710374 + 10766710375.

It is an arithmetic number, because the mean of its divisors is an integer number (10766710375).

Almost surely, 2^21533420749 is an apocalyptic number.

It is an amenable number.

21533420749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21533420749 is an equidigital number, since it uses as much as digits as its factorization.

21533420749 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 181440, while the sum is 40.

The spelling of 21533420749 in words is "twenty-one billion, five hundred thirty-three million, four hundred twenty thousand, seven hundred forty-nine".