21255217690 has 32 divisors (see below), whose sum is σ = 43977790080. Its totient is φ = 7245374784.

The previous prime is 21255217637. The next prime is 21255217703. The reversal of 21255217690 is 9671255212.

It is a happy number.

It is a super-2 number, since 2×21255217690² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 865480 + ... + 889699.

It is an arithmetic number, because the mean of its divisors is an integer number (1374305940).

Almost surely, 2^21255217690 is an apocalyptic number.

21255217690 is an abundant number, since it is smaller than the sum of its proper divisors (22722572390).

21255217690 is a wasteful number, since it uses less digits than its factorization.

21255217690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1755366.

The product of its (nonzero) digits is 75600, while the sum is 40.

The spelling of 21255217690 in words is "twenty-one billion, two hundred fifty-five million, two hundred seventeen thousand, six hundred ninety".