21681508126 has 4 divisors (see below), whose sum is σ = 32522262192. Its totient is φ = 10840754062.

The previous prime is 21681508103. The next prime is 21681508129. The reversal of 21681508126 is 62180518612.

It is a happy number.

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

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21681508129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5420377030 + ... + 5420377033.

It is an arithmetic number, because the mean of its divisors is an integer number (8130565548).

Almost surely, 2^21681508126 is an apocalyptic number.

21681508126 is a deficient number, since it is larger than the sum of its proper divisors (10840754066).

21681508126 is a wasteful number, since it uses less digits than its factorization.

21681508126 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10840754065.

The product of its (nonzero) digits is 46080, while the sum is 40.

The spelling of 21681508126 in words is "twenty-one billion, six hundred eighty-one million, five hundred eight thousand, one hundred twenty-six".