21444778645 has 8 divisors (see below), whose sum is σ = 26219276856. Its totient is φ = 16832127936.

The previous prime is 21444778633. The next prime is 21444778687. The reversal of 21444778645 is 54687744412.

It can be written as a sum of positive squares in 4 ways, for example, as 619113924 + 20825664721 = 24882^2 + 144311^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21444778645 - 2⁵ = 21444778613 is a prime.

It is a super-2 number, since 2×21444778645² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21444778592 and 21444778601.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40461582 + ... + 40462111.

It is an arithmetic number, because the mean of its divisors is an integer number (3277409607).

Almost surely, 2^21444778645 is an apocalyptic number.

It is an amenable number.

21444778645 is a deficient number, since it is larger than the sum of its proper divisors (4774498211).

21444778645 is an equidigital number, since it uses as much as digits as its factorization.

21444778645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80923751.

The product of its digits is 6021120, while the sum is 52.

The spelling of 21444778645 in words is "twenty-one billion, four hundred forty-four million, seven hundred seventy-eight thousand, six hundred forty-five".