21256645438 has 8 divisors (see below), whose sum is σ = 36439963632. Its totient is φ = 9109990896.

The previous prime is 21256645381. The next prime is 21256645477. The reversal of 21256645438 is 83454665212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 759165895 + ... + 759165922.

It is an arithmetic number, because the mean of its divisors is an integer number (4554995454).

Almost surely, 2^21256645438 is an apocalyptic number.

21256645438 is a deficient number, since it is larger than the sum of its proper divisors (15183318194).

21256645438 is a wasteful number, since it uses less digits than its factorization.

21256645438 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1518331826.

The product of its digits is 1382400, while the sum is 46.

The spelling of 21256645438 in words is "twenty-one billion, two hundred fifty-six million, six hundred forty-five thousand, four hundred thirty-eight".