21437987 has 8 divisors (see below), whose sum is σ = 21836304. Its totient is φ = 21043168.

The previous prime is 21437963. The next prime is 21438013. The reversal of 21437987 is 78973412.

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

It is a cyclic number.

It is not a de Polignac number, because 21437987 - 2¹² = 21433891 is a prime.

It is a super-2 number, since 2×21437987² = 919174573224338, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21437887) 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, 13613 + ... + 15105.

It is an arithmetic number, because the mean of its divisors is an integer number (2729538).

Almost surely, 2^21437987 is an apocalyptic number.

21437987 is a deficient number, since it is larger than the sum of its proper divisors (398317).

21437987 is a wasteful number, since it uses less digits than its factorization.

21437987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1749.

The product of its digits is 84672, while the sum is 41.

The square root of 21437987 is about 4630.1173851210. The cubic root of 21437987 is about 277.7972876549.

It can be divided in two parts, 214 and 37987, that multiplied together give a palindrome (8129218).

The spelling of 21437987 in words is "twenty-one million, four hundred thirty-seven thousand, nine hundred eighty-seven".