21420477 has 16 divisors (see below), whose sum is σ = 34175680. Its totient is φ = 13181616.

The previous prime is 21420449. The next prime is 21420479. The reversal of 21420477 is 77402412.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-21420477 is a prime.

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

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21420477.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420479) 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, 30163 + ... + 30864.

It is an arithmetic number, because the mean of its divisors is an integer number (2135980).

Almost surely, 2^21420477 is an apocalyptic number.

21420477 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21420477 is a deficient number, since it is larger than the sum of its proper divisors (12755203).

21420477 is a wasteful number, since it uses less digits than its factorization.

21420477 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61049 (or 61043 counting only the distinct ones).

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

The square root of 21420477 is about 4628.2261180716. The cubic root of 21420477 is about 277.7216344785.

Adding to 21420477 its reverse (77402412), we get a palindrome (98822889).

The spelling of 21420477 in words is "twenty-one million, four hundred twenty thousand, four hundred seventy-seven".