21115431542 has 4 divisors (see below), whose sum is σ = 31673147316. Its totient is φ = 10557715770.

The previous prime is 21115431539. The next prime is 21115431563. The reversal of 21115431542 is 24513451112.

It is a happy number.

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

It is a super-2 number, since 2×21115431542² (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 as a sum of consecutive naturals, namely, 5278857884 + ... + 5278857887.

It is an arithmetic number, because the mean of its divisors is an integer number (7918286829).

Almost surely, 2^21115431542 is an apocalyptic number.

21115431542 is a deficient number, since it is larger than the sum of its proper divisors (10557715774).

21115431542 is a wasteful number, since it uses less digits than its factorization.

21115431542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10557715773.

The product of its digits is 4800, while the sum is 29.

Adding to 21115431542 its reverse (24513451112), we get a palindrome (45628882654).

The spelling of 21115431542 in words is "twenty-one billion, one hundred fifteen million, four hundred thirty-one thousand, five hundred forty-two".