21251668 has 24 divisors (see below), whose sum is σ = 38060064. Its totient is φ = 10380000.

The previous prime is 21251617. The next prime is 21251669. The reversal of 21251668 is 86615212.

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 61071 + ... + 61417.

It is an arithmetic number, because the mean of its divisors is an integer number (1585836).

Almost surely, 2^21251668 is an apocalyptic number.

It is an amenable number.

21251668 is a deficient number, since it is larger than the sum of its proper divisors (16808396).

21251668 is a wasteful number, since it uses less digits than its factorization.

21251668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 663 (or 661 counting only the distinct ones).

The product of its digits is 5760, while the sum is 31.

The square root of 21251668 is about 4609.9531450981. The cubic root of 21251668 is about 276.9901598246.

The spelling of 21251668 in words is "twenty-one million, two hundred fifty-one thousand, six hundred sixty-eight".