21515661346 has 16 divisors (see below), whose sum is σ = 34268756184. Its totient is φ = 10096328704.

The previous prime is 21515661319. The next prime is 21515661407. The reversal of 21515661346 is 64316651512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 21145522225 + 370139121 = 145415^2 + 19239^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21515661299 and 21515661308.

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, 884335 + ... + 908338.

Almost surely, 2^21515661346 is an apocalyptic number.

21515661346 is a deficient number, since it is larger than the sum of its proper divisors (12753094838).

21515661346 is a wasteful number, since it uses less digits than its factorization.

21515661346 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1793045.

The product of its digits is 129600, while the sum is 40.

The spelling of 21515661346 in words is "twenty-one billion, five hundred fifteen million, six hundred sixty-one thousand, three hundred forty-six".