21006259638 has 64 divisors (see below), whose sum is σ = 52910280192. Its totient is φ = 5411266560.

The previous prime is 21006259607. The next prime is 21006259709. The reversal of 21006259638 is 83695260012.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a self number, because there is not a number n which added to its sum of digits gives 21006259638.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 423883 + ... + 470838.

It is an arithmetic number, because the mean of its divisors is an integer number (826723128).

Almost surely, 2^21006259638 is an apocalyptic number.

21006259638 is an abundant number, since it is smaller than the sum of its proper divisors (31904020554).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21006259638 is a wasteful number, since it uses less digits than its factorization.

21006259638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 894789.

The product of its (nonzero) digits is 155520, while the sum is 42.

The spelling of 21006259638 in words is "twenty-one billion, six million, two hundred fifty-nine thousand, six hundred thirty-eight".