21987807 has 16 divisors (see below), whose sum is σ = 31152000. Its totient is φ = 13755744.

The previous prime is 21987803. The next prime is 21987809. The reversal of 21987807 is 70878912.

It is not a de Polignac number, because 21987807 - 2² = 21987803 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21987803) 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, 4444 + ... + 7982.

It is an arithmetic number, because the mean of its divisors is an integer number (1947000).

Almost surely, 2^21987807 is an apocalyptic number.

21987807 is a deficient number, since it is larger than the sum of its proper divisors (9164193).

21987807 is a wasteful number, since it uses less digits than its factorization.

21987807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3670.

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

The square root of 21987807 is about 4689.1158015131. The cubic root of 21987807 is about 280.1521579454.

The spelling of 21987807 in words is "twenty-one million, nine hundred eighty-seven thousand, eight hundred seven".