21355770 has 16 divisors (see below), whose sum is σ = 51253920. Its totient is φ = 5694864.

The previous prime is 21355769. The next prime is 21355783. The reversal of 21355770 is 7755312.

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 711859 = 21355770 / (2 + 1 + 3 + 5 + 5 + 7 + 7 + 0).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 355900 + ... + 355959.

It is an arithmetic number, because the mean of its divisors is an integer number (3203370).

Almost surely, 2^21355770 is an apocalyptic number.

21355770 is an abundant number, since it is smaller than the sum of its proper divisors (29898150).

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

21355770 is a wasteful number, since it uses less digits than its factorization.

21355770 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 711869.

The product of its (nonzero) digits is 7350, while the sum is 30.

The square root of 21355770 is about 4621.2303556521. The cubic root of 21355770 is about 277.4417051478.

The spelling of 21355770 in words is "twenty-one million, three hundred fifty-five thousand, seven hundred seventy".