21304778529 has 4 divisors (see below), whose sum is σ = 28406371376. Its totient is φ = 14203185684.

The previous prime is 21304778431. The next prime is 21304778531. The reversal of 21304778529 is 92587740312.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21304778529 - 2⁸ = 21304778273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21304778329) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3550796419 + ... + 3550796424.

It is an arithmetic number, because the mean of its divisors is an integer number (7101592844).

Almost surely, 2^21304778529 is an apocalyptic number.

It is an amenable number.

21304778529 is a deficient number, since it is larger than the sum of its proper divisors (7101592847).

21304778529 is an equidigital number, since it uses as much as digits as its factorization.

21304778529 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7101592846.

The product of its (nonzero) digits is 846720, while the sum is 48.

The spelling of 21304778529 in words is "twenty-one billion, three hundred four million, seven hundred seventy-eight thousand, five hundred twenty-nine".