21121502506 has 8 divisors (see below), whose sum is σ = 34119350244. Its totient is φ = 9748385760.

The previous prime is 21121502471. The next prime is 21121502539. The reversal of 21121502506 is 60520512112.

It can be written as a sum of positive squares in 2 ways, for example, as 20260960281 + 860542225 = 142341^2 + 29335^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21121502506² (a number of 21 digits) contains 22 as substring.

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 in 3 ways as a sum of consecutive naturals, for example, 406182715 + ... + 406182766.

Almost surely, 2^21121502506 is an apocalyptic number.

21121502506 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21121502506 is a deficient number, since it is larger than the sum of its proper divisors (12997847738).

21121502506 is a wasteful number, since it uses less digits than its factorization.

21121502506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 812365496.

The product of its (nonzero) digits is 1200, while the sum is 25.

The spelling of 21121502506 in words is "twenty-one billion, one hundred twenty-one million, five hundred two thousand, five hundred six".