20661138 has 12 divisors (see below), whose sum is σ = 44765838. Its totient is φ = 6887040.

The previous prime is 20661131. The next prime is 20661139. The reversal of 20661138 is 83116602.

It can be written as a sum of positive squares in only one way, i.e., 19686969 + 974169 = 4437^2 + 987^2 .

It is not an unprimeable number, because it can be changed into a prime (20661131) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 573903 + ... + 573938.

Almost surely, 2^20661138 is an apocalyptic number.

20661138 is an abundant number, since it is smaller than the sum of its proper divisors (24104700).

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

20661138 is a wasteful number, since it uses less digits than its factorization.

20661138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1147849 (or 1147846 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 20661138 is about 4545.4524527268. The cubic root of 20661138 is about 274.4004038136.

The spelling of 20661138 in words is "twenty million, six hundred sixty-one thousand, one hundred thirty-eight".