21574778641 has 16 divisors (see below), whose sum is σ = 23485104720. Its totient is φ = 19700858880.

The previous prime is 21574778629. The next prime is 21574778651. The reversal of 21574778641 is 14687747512.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 1319796241 + 20254982400 = 36329^2 + 142320^2 .

It is a cyclic number.

It is not a de Polignac number, because 21574778641 - 2⁷ = 21574778513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21574778611) 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 in 15 ways as a sum of consecutive naturals, for example, 896421 + ... + 920173.

It is an arithmetic number, because the mean of its divisors is an integer number (1467819045).

Almost surely, 2^21574778641 is an apocalyptic number.

It is an amenable number.

21574778641 is a deficient number, since it is larger than the sum of its proper divisors (1910326079).

21574778641 is a wasteful number, since it uses less digits than its factorization.

21574778641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24516.

The product of its digits is 2634240, while the sum is 52.

The spelling of 21574778641 in words is "twenty-one billion, five hundred seventy-four million, seven hundred seventy-eight thousand, six hundred forty-one".