21566510542 has 4 divisors (see below), whose sum is σ = 32349765816. Its totient is φ = 10783255270.

The previous prime is 21566510503. The next prime is 21566510549. The reversal of 21566510542 is 24501566512.

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

It is a super-2 number, since 2×21566510542² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21566510549) 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, 5391627634 + ... + 5391627637.

It is an arithmetic number, because the mean of its divisors is an integer number (8087441454).

Almost surely, 2^21566510542 is an apocalyptic number.

21566510542 is a deficient number, since it is larger than the sum of its proper divisors (10783255274).

21566510542 is a wasteful number, since it uses less digits than its factorization.

21566510542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10783255273.

The product of its (nonzero) digits is 72000, while the sum is 37.

The spelling of 21566510542 in words is "twenty-one billion, five hundred sixty-six million, five hundred ten thousand, five hundred forty-two".