21998541 has 4 divisors (see below), whose sum is σ = 29331392. Its totient is φ = 14665692.

The previous prime is 21998539. The next prime is 21998567. The reversal of 21998541 is 14589912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21998541 - 2¹ = 21998539 is a prime.

It is a super-2 number, since 2×21998541² = 967871612257362, which contains 22 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 21998541.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21998531) 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, 3666421 + ... + 3666426.

It is an arithmetic number, because the mean of its divisors is an integer number (7332848).

Almost surely, 2^21998541 is an apocalyptic number.

It is an amenable number.

21998541 is a deficient number, since it is larger than the sum of its proper divisors (7332851).

21998541 is an equidigital number, since it uses as much as digits as its factorization.

21998541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7332850.

The product of its digits is 25920, while the sum is 39.

The square root of 21998541 is about 4690.2602273221. The cubic root of 21998541 is about 280.1977387235.

The spelling of 21998541 in words is "twenty-one million, nine hundred ninety-eight thousand, five hundred forty-one".