21985157 has 4 divisors (see below), whose sum is σ = 21994560. Its totient is φ = 21975756.

The previous prime is 21985153. The next prime is 21985189. The reversal of 21985157 is 75158912.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21985157 - 2² = 21985153 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 21985157.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21985151) 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, 1844 + ... + 6882.

It is an arithmetic number, because the mean of its divisors is an integer number (5498640).

Almost surely, 2^21985157 is an apocalyptic number.

It is an amenable number.

21985157 is a deficient number, since it is larger than the sum of its proper divisors (9403).

21985157 is an equidigital number, since it uses as much as digits as its factorization.

21985157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9402.

The product of its digits is 25200, while the sum is 38.

The square root of 21985157 is about 4688.8332237349. The cubic root of 21985157 is about 280.1409027219.

The spelling of 21985157 in words is "twenty-one million, nine hundred eighty-five thousand, one hundred fifty-seven".