21123401542 has 4 divisors (see below), whose sum is σ = 31685102316. Its totient is φ = 10561700770.

The previous prime is 21123401471. The next prime is 21123401543. The reversal of 21123401542 is 24510432112.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123401543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5280850384 + ... + 5280850387.

It is an arithmetic number, because the mean of its divisors is an integer number (7921275579).

Almost surely, 2^21123401542 is an apocalyptic number.

21123401542 is a deficient number, since it is larger than the sum of its proper divisors (10561700774).

21123401542 is a wasteful number, since it uses less digits than its factorization.

21123401542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10561700773.

The product of its (nonzero) digits is 1920, while the sum is 25.

Adding to 21123401542 its reverse (24510432112), we get a palindrome (45633833654).

The spelling of 21123401542 in words is "twenty-one billion, one hundred twenty-three million, four hundred one thousand, five hundred forty-two".