21506215547266 has 4 divisors (see below), whose sum is σ = 32259323320902. Its totient is φ = 10753107773632.

The previous prime is 21506215547261. The next prime is 21506215547321. The reversal of 21506215547266 is 66274551260512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 14681733305625 + 6824482241641 = 3831675^2 + 2612371^2 .

It is not an unprimeable number, because it can be changed into a prime (21506215547261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5376553886815 + ... + 5376553886818.

Almost surely, 2^{21506215547266} is an apocalyptic number.

21506215547266 is a deficient number, since it is larger than the sum of its proper divisors (10753107773636).

21506215547266 is a wasteful number, since it uses less digits than its factorization.

21506215547266 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10753107773635.

The product of its (nonzero) digits is 6048000, while the sum is 52.

The spelling of 21506215547266 in words is "twenty-one trillion, five hundred six billion, two hundred fifteen million, five hundred forty-seven thousand, two hundred sixty-six".