21145945617 has 20 divisors (see below), whose sum is σ = 31592308660. Its totient is φ = 14095547424.

The previous prime is 21145945603. The next prime is 21145945637. The reversal of 21145945617 is 71654954112.

21145945617 is a `hidden beast` number, since 2 + 1 + 1 + 4 + 594 + 56 + 1 + 7 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 14466316176 + 6679629441 = 120276^2 + 81729^2 .

It is not a de Polignac number, because 21145945617 - 2⁶ = 21145945553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21145945637) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1207359 + ... + 1224747.

It is an arithmetic number, because the mean of its divisors is an integer number (1579615433).

Almost surely, 2^21145945617 is an apocalyptic number.

21145945617 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21145945617 is a deficient number, since it is larger than the sum of its proper divisors (10446363043).

21145945617 is a wasteful number, since it uses less digits than its factorization.

21145945617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32414 (or 32405 counting only the distinct ones).

The product of its digits is 302400, while the sum is 45.

The spelling of 21145945617 in words is "twenty-one billion, one hundred forty-five million, nine hundred forty-five thousand, six hundred seventeen".