21531798 has 32 divisors (see below), whose sum is σ = 48021600. Its totient is φ = 7151328.

The previous prime is 21531793. The next prime is 21531799. The reversal of 21531798 is 89713512.

It is a super-2 number, since 2×21531798² = 927236650225608, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531793) 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, 19608 + ... + 20676.

It is an arithmetic number, because the mean of its divisors is an integer number (1500675).

Almost surely, 2^21531798 is an apocalyptic number.

21531798 is an abundant number, since it is smaller than the sum of its proper divisors (26489802).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21531798 is a wasteful number, since it uses less digits than its factorization.

21531798 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1453 (or 1447 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21531798 is about 4640.2368474034. The cubic root of 21531798 is about 278.2019046347.

The spelling of 21531798 in words is "twenty-one million, five hundred thirty-one thousand, seven hundred ninety-eight".