21021554 has 16 divisors (see below), whose sum is σ = 33638328. Its totient is φ = 9818112.

The previous prime is 21021529. The next prime is 21021569. The reversal of 21021554 is 45512012.

It can be written as a sum of positive squares in 4 ways, for example, as 14645929 + 6375625 = 3827^2 + 2525^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2402 + ... + 6914.

Almost surely, 2^21021554 is an apocalyptic number.

21021554 is a deficient number, since it is larger than the sum of its proper divisors (12616774).

21021554 is a wasteful number, since it uses less digits than its factorization.

21021554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4669.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21021554 is about 4584.9268260246. The cubic root of 21021554 is about 275.9867756039.

Adding to 21021554 its reverse (45512012), we get a palindrome (66533566).

The spelling of 21021554 in words is "twenty-one million, twenty-one thousand, five hundred fifty-four".