21490040 has 144 divisors (see below), whose sum is σ = 60675480. Its totient is φ = 6789120.

The previous prime is 21490033. The next prime is 21490043. The reversal of 21490040 is 4009412.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21489994 and 21490021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21490043) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1264112 + ... + 1264128.

Almost surely, 2^21490040 is an apocalyptic number.

21490040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21490040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30337740).

21490040 is an abundant number, since it is smaller than the sum of its proper divisors (39185440).

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

21490040 is a wasteful number, since it uses less digits than its factorization.

21490040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82 (or 48 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21490040 is about 4635.7351089121. The cubic root of 21490040 is about 278.0219433018.

Adding to 21490040 its reverse (4009412), we get a palindrome (25499452).

The spelling of 21490040 in words is "twenty-one million, four hundred ninety thousand, forty".