21087494 has 4 divisors (see below), whose sum is σ = 31631244. Its totient is φ = 10543746.

The previous prime is 21087491. The next prime is 21087529. The reversal of 21087494 is 49478012.

It is a semiprime because it is the product of two primes.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21087491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5271872 + ... + 5271875.

It is an arithmetic number, because the mean of its divisors is an integer number (7907811).

Almost surely, 2^21087494 is an apocalyptic number.

21087494 is a deficient number, since it is larger than the sum of its proper divisors (10543750).

21087494 is a wasteful number, since it uses less digits than its factorization.

21087494 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10543749.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 21087494 is about 4592.1121501984. The cubic root of 21087494 is about 276.2750443774.

The spelling of 21087494 in words is "twenty-one million, eighty-seven thousand, four hundred ninety-four".