21651555606 has 16 divisors (see below), whose sum is σ = 45850353264. Its totient is φ = 6792644864.

The previous prime is 21651555599. The next prime is 21651555617. The reversal of 21651555606 is 60655515612.

It is a Curzon number.

It is a congruent number.

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, 106134975 + ... + 106135178.

It is an arithmetic number, because the mean of its divisors is an integer number (2865647079).

Almost surely, 2^21651555606 is an apocalyptic number.

21651555606 is an abundant number, since it is smaller than the sum of its proper divisors (24198797658).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21651555606 is a wasteful number, since it uses less digits than its factorization.

21651555606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212270175.

The product of its (nonzero) digits is 270000, while the sum is 42.

The spelling of 21651555606 in words is "twenty-one billion, six hundred fifty-one million, five hundred fifty-five thousand, six hundred six".