21987903 has 8 divisors (see below), whose sum is σ = 33505408. Its totient is φ = 12564504.

The previous prime is 21987899. The next prime is 21987907. The reversal of 21987903 is 30978912.

It is an interprime number because it is at equal distance from previous prime (21987899) and next prime (21987907).

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

It is not a de Polignac number, because 21987903 - 2² = 21987899 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21987907) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 523501 + ... + 523542.

It is an arithmetic number, because the mean of its divisors is an integer number (4188176).

Almost surely, 2^21987903 is an apocalyptic number.

21987903 is a deficient number, since it is larger than the sum of its proper divisors (11517505).

21987903 is a wasteful number, since it uses less digits than its factorization.

21987903 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1047053.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 21987903 is about 4689.1260379734. The cubic root of 21987903 is about 280.1525656648.

It can be divided in two parts, 2198 and 7903, that added together give a palindrome (10101).

The spelling of 21987903 in words is "twenty-one million, nine hundred eighty-seven thousand, nine hundred three".