21390277 has 4 divisors (see below), whose sum is σ = 21661120. Its totient is φ = 21119436.

The previous prime is 21390251. The next prime is 21390283. The reversal of 21390277 is 77209312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21390277 - 2¹⁵ = 21357509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390247) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 135303 + ... + 135460.

It is an arithmetic number, because the mean of its divisors is an integer number (5415280).

Almost surely, 2^21390277 is an apocalyptic number.

It is an amenable number.

21390277 is a deficient number, since it is larger than the sum of its proper divisors (270843).

21390277 is an equidigital number, since it uses as much as digits as its factorization.

21390277 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 270842.

The product of its (nonzero) digits is 5292, while the sum is 31.

The square root of 21390277 is about 4624.9623782254. The cubic root of 21390277 is about 277.5910563397.

Adding to 21390277 its reverse (77209312), we get a palindrome (98599589).

The spelling of 21390277 in words is "twenty-one million, three hundred ninety thousand, two hundred seventy-seven".