21651596738 has 4 divisors (see below), whose sum is σ = 32477395110. Its totient is φ = 10825798368.

The previous prime is 21651596723. The next prime is 21651596773. The reversal of 21651596738 is 83769515612.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 21611058049 + 40538689 = 147007^2 + 6367^2 .

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21651596738.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5412899183 + ... + 5412899186.

Almost surely, 2^21651596738 is an apocalyptic number.

21651596738 is a deficient number, since it is larger than the sum of its proper divisors (10825798372).

21651596738 is a wasteful number, since it uses less digits than its factorization.

21651596738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10825798371.

The product of its digits is 2721600, while the sum is 53.

The spelling of 21651596738 in words is "twenty-one billion, six hundred fifty-one million, five hundred ninety-six thousand, seven hundred thirty-eight".