21521533 has 8 divisors (see below), whose sum is σ = 24235776. Its totient is φ = 18933600.

The previous prime is 21521527. The next prime is 21521557. The reversal of 21521533 is 33512512.

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

It is a cyclic number.

It is not a de Polignac number, because 21521533 - 2¹⁷ = 21390461 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521503) 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, 31216 + ... + 31897.

It is an arithmetic number, because the mean of its divisors is an integer number (3029472).

Almost surely, 2^21521533 is an apocalyptic number.

It is an amenable number.

21521533 is a deficient number, since it is larger than the sum of its proper divisors (2714243).

21521533 is a wasteful number, since it uses less digits than its factorization.

21521533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63155.

The product of its digits is 900, while the sum is 22.

The square root of 21521533 is about 4639.1306297624. The cubic root of 21521533 is about 278.1576879141.

The spelling of 21521533 in words is "twenty-one million, five hundred twenty-one thousand, five hundred thirty-three".