21106237556 has 24 divisors (see below), whose sum is σ = 37432389120. Its totient is φ = 10411476192.

The previous prime is 21106237543. The next prime is 21106237573. The reversal of 21106237556 is 65573260112.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 394166 + ... + 444498.

It is an arithmetic number, because the mean of its divisors is an integer number (1559682880).

Almost surely, 2^21106237556 is an apocalyptic number.

It is an amenable number.

21106237556 is a deficient number, since it is larger than the sum of its proper divisors (16326151564).

21106237556 is a wasteful number, since it uses less digits than its factorization.

21106237556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51743 (or 51741 counting only the distinct ones).

The product of its (nonzero) digits is 75600, while the sum is 38.

Adding to 21106237556 its reverse (65573260112), we get a palindrome (86679497668).

The spelling of 21106237556 in words is "twenty-one billion, one hundred six million, two hundred thirty-seven thousand, five hundred fifty-six".