209421721090 has 64 divisors (see below), whose sum is σ = 412141685760. Its totient is φ = 76273182720.

The previous prime is 209421721049. The next prime is 209421721097. The reversal of 209421721090 is 90127124902.

It is not an unprimeable number, because it can be changed into a prime (209421721097) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 27289494 + ... + 27297166.

It is an arithmetic number, because the mean of its divisors is an integer number (6439713840).

Almost surely, 2^209421721090 is an apocalyptic number.

209421721090 is a deficient number, since it is larger than the sum of its proper divisors (202719964670).

209421721090 is a wasteful number, since it uses less digits than its factorization.

209421721090 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12907.

The product of its (nonzero) digits is 18144, while the sum is 37.

Adding to 209421721090 its reverse (90127124902), we get a palindrome (299548845992).

The spelling of 209421721090 in words is "two hundred nine billion, four hundred twenty-one million, seven hundred twenty-one thousand, ninety".