21240655021 has 8 divisors (see below), whose sum is σ = 21663730880. Its totient is φ = 20821149792.

The previous prime is 21240655013. The next prime is 21240655091. The reversal of 21240655021 is 12055604212.

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

It is a cyclic number.

It is not a de Polignac number, because 21240655021 - 2³ = 21240655013 is a prime.

It is a super-2 number, since 2×21240655021² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21240655001) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 880641 + ... + 904438.

It is an arithmetic number, because the mean of its divisors is an integer number (2707966360).

Almost surely, 2^21240655021 is an apocalyptic number.

It is an amenable number.

21240655021 is a deficient number, since it is larger than the sum of its proper divisors (423075859).

21240655021 is a wasteful number, since it uses less digits than its factorization.

21240655021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1785315.

The product of its (nonzero) digits is 4800, while the sum is 28.

The spelling of 21240655021 in words is "twenty-one billion, two hundred forty million, six hundred fifty-five thousand, twenty-one".