21131554 has 4 divisors (see below), whose sum is σ = 31697334. Its totient is φ = 10565776.

The previous prime is 21131531. The next prime is 21131567. The reversal of 21131554 is 45513112.

It is a happy number.

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., 18258529 + 2873025 = 4273^2 + 1695^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5282887 + ... + 5282890.

Almost surely, 2^21131554 is an apocalyptic number.

21131554 is a deficient number, since it is larger than the sum of its proper divisors (10565780).

21131554 is a wasteful number, since it uses less digits than its factorization.

21131554 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10565779.

The product of its digits is 600, while the sum is 22.

The square root of 21131554 is about 4596.9070036275. The cubic root of 21131554 is about 276.4673259648.

Adding to 21131554 its reverse (45513112), we get a palindrome (66644666).

The spelling of 21131554 in words is "twenty-one million, one hundred thirty-one thousand, five hundred fifty-four".