20521404 has 48 divisors (see below), whose sum is σ = 53625600. Its totient is φ = 6786288.

The previous prime is 20521399. The next prime is 20521409. The reversal of 20521404 is 40412502.

It is an interprime number because it is at equal distance from previous prime (20521399) and next prime (20521409).

It is a super-2 number, since 2×20521404² = 842256044262432, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20521409) 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, 14329 + ... + 15695.

It is an arithmetic number, because the mean of its divisors is an integer number (1117200).

Almost surely, 2^20521404 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20521404, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26812800).

20521404 is an abundant number, since it is smaller than the sum of its proper divisors (33104196).

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

20521404 is a wasteful number, since it uses less digits than its factorization.

20521404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1519 (or 1511 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 20521404 is about 4530.0556287975. The cubic root of 20521404 is about 273.7804019528.

Adding to 20521404 its reverse (40412502), we get a palindrome (60933906).

It can be divided in two parts, 205 and 21404, that added together give a square (21609 = 147²).

The spelling of 20521404 in words is "twenty million, five hundred twenty-one thousand, four hundred four".