21420100 has 36 divisors (see below), whose sum is σ = 50060164. Its totient is φ = 7908480.

The previous prime is 21420097. The next prime is 21420103. The reversal of 21420100 is 102412.

It is an interprime number because it is at equal distance from previous prime (21420097) and next prime (21420103).

It can be written as a sum of positive squares in 6 ways, for example, as 3594816 + 17825284 = 1896^2 + 4222^2 .

It is a Harshad number since it is a multiple of its sum of digits (10).

It is not an unprimeable number, because it can be changed into a prime (21420103) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6939 + ... + 9538.

Almost surely, 2^21420100 is an apocalyptic number.

21420100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21420100 is an abundant number, since it is smaller than the sum of its proper divisors (28640064).

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

21420100 is a wasteful number, since it uses less digits than its factorization.

21420100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16504 (or 16497 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 21420100 is about 4628.1853895452. The cubic root of 21420100 is about 277.7200051704.

Adding to 21420100 its reverse (102412), we get a palindrome (21522512).

It can be divided in two parts, 21 and 420100, that multiplied together give a triangular number (8822100 = T₄₂₀₀).

The spelling of 21420100 in words is "twenty-one million, four hundred twenty thousand, one hundred".