20781564 has 24 divisors (see below), whose sum is σ = 48749568. Its totient is φ = 6890160.

The previous prime is 20781559. The next prime is 20781583. The reversal of 20781564 is 46518702.

It is a congruent number.

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, 2242 + ... + 6825.

It is an arithmetic number, because the mean of its divisors is an integer number (2031232).

Almost surely, 2^20781564 is an apocalyptic number.

It is an amenable number.

20781564 is an abundant number, since it is smaller than the sum of its proper divisors (27968004).

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

20781564 is a wasteful number, since it uses less digits than its factorization.

20781564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9265 (or 9263 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 20781564 is about 4558.6800721261. The cubic root of 20781564 is about 274.9324969303.

The spelling of 20781564 in words is "twenty million, seven hundred eighty-one thousand, five hundred sixty-four".