21508254538 has 16 divisors (see below), whose sum is σ = 33016981536. Its totient is φ = 10502659440.

The previous prime is 21508254499. The next prime is 21508254541. The reversal of 21508254538 is 83545280512.

It is a Harshad number since it is a multiple of its sum of digits (43).

It is a junction number, because it is equal to n+sod(n) for n = 21508254494 and 21508254503.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1043553 + ... + 1063963.

It is an arithmetic number, because the mean of its divisors is an integer number (2063561346).

Almost surely, 2^21508254538 is an apocalyptic number.

21508254538 is a deficient number, since it is larger than the sum of its proper divisors (11508726998).

21508254538 is a wasteful number, since it uses less digits than its factorization.

21508254538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32709.

The product of its (nonzero) digits is 384000, while the sum is 43.

The spelling of 21508254538 in words is "twenty-one billion, five hundred eight million, two hundred fifty-four thousand, five hundred thirty-eight".