21497489 has 16 divisors (see below), whose sum is σ = 24195024. Its totient is φ = 18969600.

The previous prime is 21497473. The next prime is 21497491. The reversal of 21497489 is 98479412.

It can be written as a sum of positive squares in 8 ways, for example, as 9560464 + 11937025 = 3092^2 + 3455^2 .

It is not a de Polignac number, because 21497489 - 2⁴ = 21497473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21497429) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27869 + ... + 28629.

It is an arithmetic number, because the mean of its divisors is an integer number (1512189).

Almost surely, 2^21497489 is an apocalyptic number.

It is an amenable number.

21497489 is a deficient number, since it is larger than the sum of its proper divisors (2697535).

21497489 is a wasteful number, since it uses less digits than its factorization.

21497489 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 868.

The product of its digits is 145152, while the sum is 44.

The square root of 21497489 is about 4636.5384717481. The cubic root of 21497489 is about 278.0540627738.

The spelling of 21497489 in words is "twenty-one million, four hundred ninety-seven thousand, four hundred eighty-nine".