21237641 has 4 divisors (see below), whose sum is σ = 22486932. Its totient is φ = 19988352.

The previous prime is 21237637. The next prime is 21237661. The reversal of 21237641 is 14673212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 18361225 + 2876416 = 4285^2 + 1696^2 .

It is a cyclic number.

It is not a de Polignac number, because 21237641 - 2² = 21237637 is a prime.

It is a super-3 number, since 3×21237641³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21237641.

It is not an unprimeable number, because it can be changed into a prime (21237661) 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, 624620 + ... + 624653.

It is an arithmetic number, because the mean of its divisors is an integer number (5621733).

Almost surely, 2^21237641 is an apocalyptic number.

It is an amenable number.

21237641 is a deficient number, since it is larger than the sum of its proper divisors (1249291).

21237641 is a wasteful number, since it uses less digits than its factorization.

21237641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1249290.

The product of its digits is 2016, while the sum is 26.

The square root of 21237641 is about 4608.4315119138. The cubic root of 21237641 is about 276.9292046701.

The spelling of 21237641 in words is "twenty-one million, two hundred thirty-seven thousand, six hundred forty-one".