21453633765 has 12 divisors (see below), whose sum is σ = 37186298604. Its totient is φ = 11441937984.

The previous prime is 21453633737. The next prime is 21453633767. The reversal of 21453633765 is 56733635412.

It is a happy number.

21453633765 is a `hidden beast` number, since 2 + 1 + 4 + 5 + 3 + 633 + 7 + 6 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 3732965604 + 17720668161 = 61098^2 + 133119^2 .

It is not a de Polignac number, because 21453633765 - 2¹³ = 21453625573 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 476747417 = 21453633765 / (2 + 1 + 4 + 5 + 3 + 6 + 3 + 3 + 7 + 6 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 21453633765.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21453633767) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 238373664 + ... + 238373753.

It is an arithmetic number, because the mean of its divisors is an integer number (3098858217).

Almost surely, 2^21453633765 is an apocalyptic number.

It is an amenable number.

21453633765 is a deficient number, since it is larger than the sum of its proper divisors (15732664839).

21453633765 is a wasteful number, since it uses less digits than its factorization.

21453633765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 476747428 (or 476747425 counting only the distinct ones).

The product of its digits is 1360800, while the sum is 45.

The spelling of 21453633765 in words is "twenty-one billion, four hundred fifty-three million, six hundred thirty-three thousand, seven hundred sixty-five".