21221057406518 has 8 divisors (see below), whose sum is σ = 31839890735448. Its totient is φ = 10607760494704.

The previous prime is 21221057406473. The next prime is 21221057406539. The reversal of 21221057406518 is 81560475012212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1384094696 + ... + 1384110027.

It is an arithmetic number, because the mean of its divisors is an integer number (3979986341931).

Almost surely, 2^{21221057406518} is an apocalyptic number.

21221057406518 is a deficient number, since it is larger than the sum of its proper divisors (10618833328930).

21221057406518 is a wasteful number, since it uses less digits than its factorization.

21221057406518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2768208558.

The product of its (nonzero) digits is 268800, while the sum is 44.

The spelling of 21221057406518 in words is "twenty-one trillion, two hundred twenty-one billion, fifty-seven million, four hundred six thousand, five hundred eighteen".