21660554 has 4 divisors (see below), whose sum is σ = 32490834. Its totient is φ = 10830276.

The previous prime is 21660523. The next prime is 21660559. The reversal of 21660554 is 45506612.

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., 20912329 + 748225 = 4573^2 + 865^2 .

It is not an unprimeable number, because it can be changed into a prime (21660559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5415137 + ... + 5415140.

Almost surely, 2^21660554 is an apocalyptic number.

21660554 is a deficient number, since it is larger than the sum of its proper divisors (10830280).

21660554 is a wasteful number, since it uses less digits than its factorization.

21660554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10830279.

The product of its (nonzero) digits is 7200, while the sum is 29.

The square root of 21660554 is about 4654.0900292109. The cubic root of 21660554 is about 278.7553342099.

The spelling of 21660554 in words is "twenty-one million, six hundred sixty thousand, five hundred fifty-four".