20121221138 has 4 divisors (see below), whose sum is σ = 30181831710. Its totient is φ = 10060610568.

The previous prime is 20121221137. The next prime is 20121221161. The reversal of 20121221138 is 83112212102.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 19297932889 + 823288249 = 138917^2 + 28693^2 .

It is not an unprimeable number, because it can be changed into a prime (20121221137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5030305283 + ... + 5030305286.

Almost surely, 2^20121221138 is an apocalyptic number.

20121221138 is a deficient number, since it is larger than the sum of its proper divisors (10060610572).

20121221138 is a wasteful number, since it uses less digits than its factorization.

20121221138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10060610571.

The product of its (nonzero) digits is 384, while the sum is 23.

The spelling of 20121221138 in words is "twenty billion, one hundred twenty-one million, two hundred twenty-one thousand, one hundred thirty-eight".