21497387 has 4 divisors (see below), whose sum is σ = 22432080. Its totient is φ = 20562696.

The previous prime is 21497369. The next prime is 21497429. The reversal of 21497387 is 78379412.

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

It is a cyclic number.

It is not a de Polignac number, because 21497387 - 2⁸ = 21497131 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21497317) 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, 467312 + ... + 467357.

It is an arithmetic number, because the mean of its divisors is an integer number (5608020).

Almost surely, 2^21497387 is an apocalyptic number.

21497387 is a deficient number, since it is larger than the sum of its proper divisors (934693).

21497387 is an equidigital number, since it uses as much as digits as its factorization.

21497387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 934692.

The product of its digits is 84672, while the sum is 41.

The square root of 21497387 is about 4636.5274721498. The cubic root of 21497387 is about 278.0536230084.

The spelling of 21497387 in words is "twenty-one million, four hundred ninety-seven thousand, three hundred eighty-seven".