21510157 has 2 divisors, whose sum is σ = 21510158. Its totient is φ = 21510156.

The previous prime is 21510133. The next prime is 21510173. The reversal of 21510157 is 75101512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19945156 + 1565001 = 4466^2 + 1251^2 .

It is a cyclic number.

It is not a de Polignac number, because 21510157 - 2⁷ = 21510029 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21510127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10755078 + 10755079.

It is an arithmetic number, because the mean of its divisors is an integer number (10755079).

Almost surely, 2^21510157 is an apocalyptic number.

It is an amenable number.

21510157 is a deficient number, since it is larger than the sum of its proper divisors (1).

21510157 is an equidigital number, since it uses as much as digits as its factorization.

21510157 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 350, while the sum is 22.

The square root of 21510157 is about 4637.9043759008. The cubic root of 21510157 is about 278.1086691080.

Adding to 21510157 its reverse (75101512), we get a palindrome (96611669).

The spelling of 21510157 in words is "twenty-one million, five hundred ten thousand, one hundred fifty-seven".