21660157 has 4 divisors (see below), whose sum is σ = 21874716. Its totient is φ = 21445600.

The previous prime is 21660151. The next prime is 21660161. The reversal of 21660157 is 75106612.

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

It can be written as a sum of positive squares in 2 ways, for example, as 20848356 + 811801 = 4566^2 + 901^2 .

It is a cyclic number.

It is not a de Polignac number, because 21660157 - 2²³ = 13271549 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 (21660151) 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, 107128 + ... + 107329.

It is an arithmetic number, because the mean of its divisors is an integer number (5468679).

Almost surely, 2^21660157 is an apocalyptic number.

It is an amenable number.

21660157 is a deficient number, since it is larger than the sum of its proper divisors (214559).

21660157 is a wasteful number, since it uses less digits than its factorization.

21660157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214558.

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

The square root of 21660157 is about 4654.0473783579. The cubic root of 21660157 is about 278.7536311672.

Adding to 21660157 its reverse (75106612), we get a palindrome (96766769).

The spelling of 21660157 in words is "twenty-one million, six hundred sixty thousand, one hundred fifty-seven".