20661157 has 4 divisors (see below), whose sum is σ = 22539456. Its totient is φ = 18782860.

The previous prime is 20661143. The next prime is 20661191. The reversal of 20661157 is 75116602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20661157 - 2²³ = 12272549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20661257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 939133 + ... + 939154.

It is an arithmetic number, because the mean of its divisors is an integer number (5634864).

Almost surely, 2^20661157 is an apocalyptic number.

It is an amenable number.

20661157 is a deficient number, since it is larger than the sum of its proper divisors (1878299).

20661157 is a wasteful number, since it uses less digits than its factorization.

20661157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1878298.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 20661157 is about 4545.4545427273. The cubic root of 20661157 is about 274.4004879265.

Adding to 20661157 its reverse (75116602), we get a palindrome (95777759).

Subtracting 20661157 from its reverse (75116602), we obtain a palindrome (54455445).

It can be divided in two parts, 2066 and 1157, that added together give a palindrome (3223).

The spelling of 20661157 in words is "twenty million, six hundred sixty-one thousand, one hundred fifty-seven".