21511642 has 4 divisors (see below), whose sum is σ = 32267466. Its totient is φ = 10755820.

The previous prime is 21511631. The next prime is 21511657. The reversal of 21511642 is 24611512.

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., 16719921 + 4791721 = 4089^2 + 2189^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5377909 + ... + 5377912.

Almost surely, 2^21511642 is an apocalyptic number.

21511642 is a deficient number, since it is larger than the sum of its proper divisors (10755824).

21511642 is a wasteful number, since it uses less digits than its factorization.

21511642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10755823.

The product of its digits is 480, while the sum is 22.

The square root of 21511642 is about 4638.0644669948. The cubic root of 21511642 is about 278.1150689043.

The spelling of 21511642 in words is "twenty-one million, five hundred eleven thousand, six hundred forty-two".