21521433 has 16 divisors (see below), whose sum is σ = 30945600. Its totient is φ = 13259520.

The previous prime is 21521431. The next prime is 21521453. The reversal of 21521433 is 33412512.

It is not a de Polignac number, because 21521433 - 2¹ = 21521431 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21521431) 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, 2268 + ... + 6941.

It is an arithmetic number, because the mean of its divisors is an integer number (1934100).

Almost surely, 2^21521433 is an apocalyptic number.

It is an amenable number.

21521433 is a deficient number, since it is larger than the sum of its proper divisors (9424167).

21521433 is a wasteful number, since it uses less digits than its factorization.

21521433 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9272.

The product of its digits is 720, while the sum is 21.

The square root of 21521433 is about 4639.1198518685. The cubic root of 21521433 is about 278.1572570927.

Adding to 21521433 its reverse (33412512), we get a palindrome (54933945).

The spelling of 21521433 in words is "twenty-one million, five hundred twenty-one thousand, four hundred thirty-three".