21987497 has 8 divisors (see below), whose sum is σ = 25177152. Its totient is φ = 18810000.

The previous prime is 21987487. The next prime is 21987523. The reversal of 21987497 is 79478912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21987497 - 2²⁴ = 5210281 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21987487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1247 + ... + 6747.

It is an arithmetic number, because the mean of its divisors is an integer number (3147144).

Almost surely, 2^21987497 is an apocalyptic number.

It is an amenable number.

21987497 is a deficient number, since it is larger than the sum of its proper divisors (3189655).

21987497 is an equidigital number, since it uses as much as digits as its factorization.

21987497 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6079.

The product of its digits is 254016, while the sum is 47.

The square root of 21987497 is about 4689.0827461242. The cubic root of 21987497 is about 280.1508413433.

The spelling of 21987497 in words is "twenty-one million, nine hundred eighty-seven thousand, four hundred ninety-seven".