21201917945 has 8 divisors (see below), whose sum is σ = 27399401736. Its totient is φ = 15656800896.

The previous prime is 21201917927. The next prime is 21201917959. The reversal of 21201917945 is 54971910212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1403176681 + 19798741264 = 37459^2 + 140708^2 .

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 21201917945 - 2¹² = 21201913849 is a prime.

It is a Duffinian 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, 163091612 + ... + 163091741.

It is an arithmetic number, because the mean of its divisors is an integer number (3424925217).

Almost surely, 2^21201917945 is an apocalyptic number.

It is an amenable number.

21201917945 is a deficient number, since it is larger than the sum of its proper divisors (6197483791).

21201917945 is a wasteful number, since it uses less digits than its factorization.

21201917945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 326183371.

The product of its (nonzero) digits is 45360, while the sum is 41.

The spelling of 21201917945 in words is "twenty-one billion, two hundred one million, nine hundred seventeen thousand, nine hundred forty-five".