21498981 has 16 divisors (see below), whose sum is σ = 33177600. Its totient is φ = 12128688.

The previous prime is 21498977. The next prime is 21498989. The reversal of 21498981 is 18989412.

It is not a de Polignac number, because 21498981 - 2² = 21498977 is a prime.

It is a super-2 number, since 2×21498981² = 924412368076722, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21498989) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4821 + ... + 8138.

It is an arithmetic number, because the mean of its divisors is an integer number (2073600).

Almost surely, 2^21498981 is an apocalyptic number.

21498981 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21498981 is a deficient number, since it is larger than the sum of its proper divisors (11678619).

21498981 is a wasteful number, since it uses less digits than its factorization.

21498981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13048.

The product of its digits is 41472, while the sum is 42.

The square root of 21498981 is about 4636.6993648500. The cubic root of 21498981 is about 278.0604952625.

The spelling of 21498981 in words is "twenty-one million, four hundred ninety-eight thousand, nine hundred eighty-one".