21402756 has 18 divisors (see below), whose sum is σ = 54101502. Its totient is φ = 7134240.

The previous prime is 21402739. The next prime is 21402763. The reversal of 21402756 is 65720412.

It can be written as a sum of positive squares in only one way, i.e., 19660356 + 1742400 = 4434^2 + 1320^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 297225 + ... + 297296.

It is an arithmetic number, because the mean of its divisors is an integer number (3005639).

Almost surely, 2^21402756 is an apocalyptic number.

It is an amenable number.

21402756 is an abundant number, since it is smaller than the sum of its proper divisors (32698746).

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

21402756 is a wasteful number, since it uses less digits than its factorization.

21402756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 594531 (or 594526 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21402756 is about 4626.3112735742. The cubic root of 21402756 is about 277.6450276740.

The spelling of 21402756 in words is "twenty-one million, four hundred two thousand, seven hundred fifty-six".