21729392749 has 4 divisors (see below), whose sum is σ = 22259377980. Its totient is φ = 21199407520.

The previous prime is 21729392701. The next prime is 21729392753. The reversal of 21729392749 is 94729392712.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8106301225 + 13623091524 = 90035^2 + 116718^2 .

It is not a de Polignac number, because 21729392749 - 2¹⁷ = 21729261677 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21729392749.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21729392149) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 264992554 + ... + 264992635.

It is an arithmetic number, because the mean of its divisors is an integer number (5564844495).

Almost surely, 2^21729392749 is an apocalyptic number.

It is an amenable number.

21729392749 is a deficient number, since it is larger than the sum of its proper divisors (529985231).

21729392749 is an equidigital number, since it uses as much as digits as its factorization.

21729392749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 529985230.

The product of its digits is 3429216, while the sum is 55.

The spelling of 21729392749 in words is "twenty-one billion, seven hundred twenty-nine million, three hundred ninety-two thousand, seven hundred forty-nine".