21991654 has 4 divisors (see below), whose sum is σ = 32987484. Its totient is φ = 10995826.

The previous prime is 21991649. The next prime is 21991691. The reversal of 21991654 is 45619912.

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

It is a congruent number.

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, 5497912 + ... + 5497915.

It is an arithmetic number, because the mean of its divisors is an integer number (8246871).

Almost surely, 2^21991654 is an apocalyptic number.

21991654 is a deficient number, since it is larger than the sum of its proper divisors (10995830).

21991654 is a wasteful number, since it uses less digits than its factorization.

21991654 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10995829.

The product of its digits is 19440, while the sum is 37.

The square root of 21991654 is about 4689.5259888394. The cubic root of 21991654 is about 280.1684955229.

The spelling of 21991654 in words is "twenty-one million, nine hundred ninety-one thousand, six hundred fifty-four".