21499157 has 4 divisors (see below), whose sum is σ = 21793740. Its totient is φ = 21204576.

The previous prime is 21499141. The next prime is 21499171. The reversal of 21499157 is 75199412.

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 4268356 + 17230801 = 2066^2 + 4151^2 .

It is a cyclic number.

It is not a de Polignac number, because 21499157 - 2⁴ = 21499141 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21499157.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21499057) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 147182 + ... + 147327.

It is an arithmetic number, because the mean of its divisors is an integer number (5448435).

Almost surely, 2^21499157 is an apocalyptic number.

It is an amenable number.

21499157 is a deficient number, since it is larger than the sum of its proper divisors (294583).

21499157 is an equidigital number, since it uses as much as digits as its factorization.

21499157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 294582.

The product of its digits is 22680, while the sum is 38.

The square root of 21499157 is about 4636.7183438290. The cubic root of 21499157 is about 278.0612540351.

The spelling of 21499157 in words is "twenty-one million, four hundred ninety-nine thousand, one hundred fifty-seven".