21205072838 has 8 divisors (see below), whose sum is σ = 31920004488. Its totient is φ = 10565071344.

The previous prime is 21205072813. The next prime is 21205072841. The reversal of 21205072838 is 83827050212.

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

It is a super-2 number, since 2×21205072838² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18731831 + ... + 18732962.

It is an arithmetic number, because the mean of its divisors is an integer number (3990000561).

Almost surely, 2^21205072838 is an apocalyptic number.

21205072838 is a deficient number, since it is larger than the sum of its proper divisors (10714931650).

21205072838 is a wasteful number, since it uses less digits than its factorization.

21205072838 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37465078.

The product of its (nonzero) digits is 53760, while the sum is 38.

The spelling of 21205072838 in words is "twenty-one billion, two hundred five million, seventy-two thousand, eight hundred thirty-eight".