20661156 has 60 divisors (see below), whose sum is σ = 55305712. Its totient is φ = 6722352.

The previous prime is 20661143. The next prime is 20661191. The reversal of 20661156 is 65116602.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 13191 + ... + 14673.

Almost surely, 2^20661156 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20661156, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27652856).

20661156 is an abundant number, since it is smaller than the sum of its proper divisors (34644556).

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

20661156 is a wasteful number, since it uses less digits than its factorization.

20661156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1542 (or 1531 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 20661156 is about 4545.4544327273. The cubic root of 20661156 is about 274.4004834995.

Adding to 20661156 its reverse (65116602), we get a palindrome (85777758).

The spelling of 20661156 in words is "twenty million, six hundred sixty-one thousand, one hundred fifty-six".