21991054742 has 4 divisors (see below), whose sum is σ = 32986582116. Its totient is φ = 10995527370.

The previous prime is 21991054741. The next prime is 21991054781. The reversal of 21991054742 is 24745019912.

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

It is a junction number, because it is equal to n+sod(n) for n = 21991054693 and 21991054702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21991054741) by changing a digit.

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 as a sum of consecutive naturals, namely, 5497763684 + ... + 5497763687.

It is an arithmetic number, because the mean of its divisors is an integer number (8246645529).

Almost surely, 2^21991054742 is an apocalyptic number.

21991054742 is a deficient number, since it is larger than the sum of its proper divisors (10995527374).

21991054742 is a wasteful number, since it uses less digits than its factorization.

21991054742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10995527373.

The product of its (nonzero) digits is 181440, while the sum is 44.

The spelling of 21991054742 in words is "twenty-one billion, nine hundred ninety-one million, fifty-four thousand, seven hundred forty-two".