21210999990 has 64 divisors (see below), whose sum is σ = 52467768576. Its totient is φ = 5483866752.

The previous prime is 21210999989. The next prime is 21211000073. The reversal of 21210999990 is 9999901212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 280369 + ... + 347891.

It is an arithmetic number, because the mean of its divisors is an integer number (819808884).

Almost surely, 2^21210999990 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21210999990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26233884288).

21210999990 is an abundant number, since it is smaller than the sum of its proper divisors (31256768586).

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

21210999990 is a wasteful number, since it uses less digits than its factorization.

21210999990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67853.

The product of its (nonzero) digits is 236196, while the sum is 51.

The spelling of 21210999990 in words is "twenty-one billion, two hundred ten million, nine hundred ninety-nine thousand, nine hundred ninety".