21645770 has 32 divisors (see below), whose sum is σ = 40487040. Its totient is φ = 8326080.

The previous prime is 21645761. The next prime is 21645787. The reversal of 21645770 is 7754612.

21645770 = T₂₉₄₀ + T₂₉₄₁ + ... + T₂₉₄₄.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30176 + ... + 30884.

It is an arithmetic number, because the mean of its divisors is an integer number (1265220).

Almost surely, 2^21645770 is an apocalyptic number.

21645770 is a deficient number, since it is larger than the sum of its proper divisors (18841270).

21645770 is a wasteful number, since it uses less digits than its factorization.

21645770 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 830.

The product of its (nonzero) digits is 11760, while the sum is 32.

The square root of 21645770 is about 4652.5014776999. The cubic root of 21645770 is about 278.6919000550.

The spelling of 21645770 in words is "twenty-one million, six hundred forty-five thousand, seven hundred seventy".