20981787 has 16 divisors (see below), whose sum is σ = 29010432. Its totient is φ = 13479840.

The previous prime is 20981783. The next prime is 20981789. The reversal of 20981787 is 78718902.

It is not a de Polignac number, because 20981787 - 2² = 20981783 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20981783) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8337 + ... + 10557.

It is an arithmetic number, because the mean of its divisors is an integer number (1813152).

Almost surely, 2^20981787 is an apocalyptic number.

20981787 is a deficient number, since it is larger than the sum of its proper divisors (8028645).

20981787 is a wasteful number, since it uses less digits than its factorization.

20981787 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2338.

The product of its (nonzero) digits is 56448, while the sum is 42.

The square root of 20981787 is about 4580.5880626837. The cubic root of 20981787 is about 275.8126353848.

The spelling of 20981787 in words is "twenty million, nine hundred eighty-one thousand, seven hundred eighty-seven".