21523649 has 8 divisors (see below), whose sum is σ = 26045568. Its totient is φ = 17363520.

The previous prime is 21523631. The next prime is 21523651. The reversal of 21523649 is 94632512.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21523649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21523609) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 90317 + ... + 90554.

It is an arithmetic number, because the mean of its divisors is an integer number (3255696).

Almost surely, 2^21523649 is an apocalyptic number.

It is an amenable number.

21523649 is a deficient number, since it is larger than the sum of its proper divisors (4521919).

21523649 is a wasteful number, since it uses less digits than its factorization.

21523649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 180895.

The product of its digits is 12960, while the sum is 32.

The square root of 21523649 is about 4639.3586841287. The cubic root of 21523649 is about 278.1668037824.

The spelling of 21523649 in words is "twenty-one million, five hundred twenty-three thousand, six hundred forty-nine".