21201266644 has 24 divisors (see below), whose sum is σ = 39299337000. Its totient is φ = 9973349376.

The previous prime is 21201266633. The next prime is 21201266687. The reversal of 21201266644 is 44666210212.

It can be written as a sum of positive squares in 4 ways, for example, as 468722500 + 20732544144 = 21650^2 + 143988^2 .

It is a Harshad number since it is a multiple of its sum of digits (34).

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, 130224 + ... + 243640.

It is an arithmetic number, because the mean of its divisors is an integer number (1637472375).

Almost surely, 2^21201266644 is an apocalyptic number.

It is an amenable number.

21201266644 is a deficient number, since it is larger than the sum of its proper divisors (18098070356).

21201266644 is a wasteful number, since it uses less digits than its factorization.

21201266644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116187 (or 116185 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 34.

Adding to 21201266644 its reverse (44666210212), we get a palindrome (65867476856).

The spelling of 21201266644 in words is "twenty-one billion, two hundred one million, two hundred sixty-six thousand, six hundred forty-four".