21553066 has 4 divisors (see below), whose sum is σ = 32329602. Its totient is φ = 10776532.

The previous prime is 21553057. The next prime is 21553079. The reversal of 21553066 is 66035512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 17264025 + 4289041 = 4155^2 + 2071^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5388265 + ... + 5388268.

Almost surely, 2^21553066 is an apocalyptic number.

21553066 is a deficient number, since it is larger than the sum of its proper divisors (10776536).

21553066 is a wasteful number, since it uses less digits than its factorization.

21553066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10776535.

The product of its (nonzero) digits is 5400, while the sum is 28.

The square root of 21553066 is about 4642.5279751446. The cubic root of 21553066 is about 278.2934723256.

Adding to 21553066 its reverse (66035512), we get a palindrome (87588578).

The spelling of 21553066 in words is "twenty-one million, five hundred fifty-three thousand, sixty-six".