21996521 has 8 divisors (see below), whose sum is σ = 23832864. Its totient is φ = 20220480.

The previous prime is 21996503. The next prime is 21996551. The reversal of 21996521 is 12569912.

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

It is not a de Polignac number, because 21996521 - 2¹⁴ = 21980137 is a prime.

It is a super-2 number, since 2×21996521² = 967693872206882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21996551) 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, 14315 + ... + 15776.

It is an arithmetic number, because the mean of its divisors is an integer number (2979108).

Almost surely, 2^21996521 is an apocalyptic number.

It is an amenable number.

21996521 is a deficient number, since it is larger than the sum of its proper divisors (1836343).

21996521 is a wasteful number, since it uses less digits than its factorization.

21996521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30151.

The product of its digits is 9720, while the sum is 35.

The square root of 21996521 is about 4690.0448825145. The cubic root of 21996521 is about 280.1891621432.

The spelling of 21996521 in words is "twenty-one million, nine hundred ninety-six thousand, five hundred twenty-one".