21671554 has 4 divisors (see below), whose sum is σ = 32507334. Its totient is φ = 10835776.

The previous prime is 21671539. The next prime is 21671557. The reversal of 21671554 is 45517612.

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., 15800625 + 5870929 = 3975^2 + 2423^2 .

It is not an unprimeable number, because it can be changed into a prime (21671557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5417887 + ... + 5417890.

Almost surely, 2^21671554 is an apocalyptic number.

21671554 is a deficient number, since it is larger than the sum of its proper divisors (10835780).

21671554 is a wasteful number, since it uses less digits than its factorization.

21671554 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10835779.

The product of its digits is 8400, while the sum is 31.

The square root of 21671554 is about 4655.2716354688. The cubic root of 21671554 is about 278.8025135166.

It can be divided in two parts, 2167 and 1554, that added together give a square (3721 = 61²).

The spelling of 21671554 in words is "twenty-one million, six hundred seventy-one thousand, five hundred fifty-four".