21645131603 has 4 divisors (see below), whose sum is σ = 21999969888. Its totient is φ = 21290293320.

The previous prime is 21645131597. The next prime is 21645131623. The reversal of 21645131603 is 30613154612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21645131603 - 2²⁸ = 21376696147 is a prime.

It is a super-2 number, since 2×21645131603² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21645131603.

It is not an unprimeable number, because it can be changed into a prime (21645131623) 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, 177419051 + ... + 177419172.

It is an arithmetic number, because the mean of its divisors is an integer number (5499992472).

Almost surely, 2^21645131603 is an apocalyptic number.

21645131603 is a deficient number, since it is larger than the sum of its proper divisors (354838285).

21645131603 is an equidigital number, since it uses as much as digits as its factorization.

21645131603 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 354838284.

The product of its (nonzero) digits is 12960, while the sum is 32.

The spelling of 21645131603 in words is "twenty-one billion, six hundred forty-five million, one hundred thirty-one thousand, six hundred three".