21497188 has 6 divisors (see below), whose sum is σ = 37620086. Its totient is φ = 10748592.

The previous prime is 21497183. The next prime is 21497191. The reversal of 21497188 is 88179412.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 18249984 + 3247204 = 4272^2 + 1802^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21497188.

It is not an unprimeable number, because it can be changed into a prime (21497183) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2687145 + ... + 2687152.

Almost surely, 2^21497188 is an apocalyptic number.

It is an amenable number.

21497188 is a deficient number, since it is larger than the sum of its proper divisors (16122898).

21497188 is a wasteful number, since it uses less digits than its factorization.

21497188 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5374301 (or 5374299 counting only the distinct ones).

The product of its digits is 32256, while the sum is 40.

The square root of 21497188 is about 4636.5060120742. The cubic root of 21497188 is about 278.0527650306.

The spelling of 21497188 in words is "twenty-one million, four hundred ninety-seven thousand, one hundred eighty-eight".