21951684 has 36 divisors (see below), whose sum is σ = 56255836. Its totient is φ = 7216128.

The previous prime is 21951667. The next prime is 21951691. The reversal of 21951684 is 48615912.

It can be written as a sum of positive squares in 2 ways, for example, as 13483584 + 8468100 = 3672^2 + 2910^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

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 in 11 ways as a sum of consecutive naturals, for example, 1549 + ... + 6804.

Almost surely, 2^21951684 is an apocalyptic number.

It is an amenable number.

21951684 is an abundant number, since it is smaller than the sum of its proper divisors (34304152).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21951684 is a wasteful number, since it uses less digits than its factorization.

21951684 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8436 (or 8431 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 21951684 is about 4685.2624259480. The cubic root of 21951684 is about 279.9986564561.

The spelling of 21951684 in words is "twenty-one million, nine hundred fifty-one thousand, six hundred eighty-four".