21554021 has 8 divisors (see below), whose sum is σ = 22520064. Its totient is φ = 20604960.

The previous prime is 21553997. The next prime is 21554033. The reversal of 21554021 is 12045512.

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 21554021 - 2⁶ = 21553957 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21553984 and 21554002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21554041) 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, 1616 + ... + 6761.

It is an arithmetic number, because the mean of its divisors is an integer number (2815008).

Almost surely, 2^21554021 is an apocalyptic number.

It is an amenable number.

21554021 is a deficient number, since it is larger than the sum of its proper divisors (966043).

21554021 is an equidigital number, since it uses as much as digits as its factorization.

21554021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8491.

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

The square root of 21554021 is about 4642.6308274512. The cubic root of 21554021 is about 278.2975825891.

Adding to 21554021 its reverse (12045512), we get a palindrome (33599533).

The spelling of 21554021 in words is "twenty-one million, five hundred fifty-four thousand, twenty-one".