21420747 has 16 divisors (see below), whose sum is σ = 31848960. Its totient is φ = 14229000.

The previous prime is 21420719. The next prime is 21420761. The reversal of 21420747 is 74702412.

It is a happy number.

It is not a de Polignac number, because 21420747 - 2⁶ = 21420683 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21420747.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21421747) 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, 7122 + ... + 9672.

It is an arithmetic number, because the mean of its divisors is an integer number (1990560).

Almost surely, 2^21420747 is an apocalyptic number.

21420747 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21420747 is a deficient number, since it is larger than the sum of its proper divisors (10428213).

21420747 is a wasteful number, since it uses less digits than its factorization.

21420747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2871 (or 2865 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 27.

The square root of 21420747 is about 4628.2552868225. The cubic root of 21420747 is about 277.7228013452.

The spelling of 21420747 in words is "twenty-one million, four hundred twenty thousand, seven hundred forty-seven".