21010556642 has 4 divisors (see below), whose sum is σ = 31515834966. Its totient is φ = 10505278320.

The previous prime is 21010556639. The next prime is 21010556657. The reversal of 21010556642 is 24665501012.

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

It can be written as a sum of positive squares in only one way, i.e., 12863869561 + 8146687081 = 113419^2 + 90259^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21010556599 and 21010556608.

It is an unprimeable number.

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, 5252639159 + ... + 5252639162.

Almost surely, 2^21010556642 is an apocalyptic number.

21010556642 is a deficient number, since it is larger than the sum of its proper divisors (10505278324).

21010556642 is a wasteful number, since it uses less digits than its factorization.

21010556642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10505278323.

The product of its (nonzero) digits is 14400, while the sum is 32.

The spelling of 21010556642 in words is "twenty-one billion, ten million, five hundred fifty-six thousand, six hundred forty-two".