21615406893 has 6 divisors (see below), whose sum is σ = 31222254414. Its totient is φ = 14410271256.

The previous prime is 21615406849. The next prime is 21615406903. The reversal of 21615406893 is 39860451612.

21615406893 is a `hidden beast` number, since 2 + 16 + 1 + 540 + 6 + 8 + 93 = 666.

It can be written as a sum of positive squares in only one way, i.e., 18886180329 + 2729226564 = 137427^2 + 52242^2 .

It is not a de Polignac number, because 21615406893 - 2¹⁰ = 21615405869 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21615406193) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1200855930 + ... + 1200855947.

It is an arithmetic number, because the mean of its divisors is an integer number (5203709069).

Almost surely, 2^21615406893 is an apocalyptic number.

It is an amenable number.

21615406893 is a deficient number, since it is larger than the sum of its proper divisors (9606847521).

21615406893 is a wasteful number, since it uses less digits than its factorization.

21615406893 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2401711883 (or 2401711880 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The spelling of 21615406893 in words is "twenty-one billion, six hundred fifteen million, four hundred six thousand, eight hundred ninety-three".