21987806 has 8 divisors (see below), whose sum is σ = 33352560. Its totient is φ = 10870288.

The previous prime is 21987803. The next prime is 21987809. The reversal of 21987806 is 60878912.

It is an interprime number because it is at equal distance from previous prime (21987803) and next prime (21987809).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21987806² = 966927225387272, which contains 22 as substring.

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 3 ways as a sum of consecutive naturals, for example, 61586 + ... + 61941.

It is an arithmetic number, because the mean of its divisors is an integer number (4169070).

Almost surely, 2^21987806 is an apocalyptic number.

21987806 is a deficient number, since it is larger than the sum of its proper divisors (11364754).

21987806 is a wasteful number, since it uses less digits than its factorization.

21987806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123618.

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 21987806 is about 4689.1156948832. The cubic root of 21987806 is about 280.1521536983.

The spelling of 21987806 in words is "twenty-one million, nine hundred eighty-seven thousand, eight hundred six".