21380356 has 24 divisors (see below), whose sum is σ = 39818520. Its totient is φ = 10010112.

The previous prime is 21380341. The next prime is 21380369. The reversal of 21380356 is 65308312.

It can be written as a sum of positive squares in 4 ways, for example, as 17640000 + 3740356 = 4200^2 + 1934^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14886 + ... + 16258.

It is an arithmetic number, because the mean of its divisors is an integer number (1659105).

Almost surely, 2^21380356 is an apocalyptic number.

It is an amenable number.

21380356 is a deficient number, since it is larger than the sum of its proper divisors (18438164).

21380356 is a wasteful number, since it uses less digits than its factorization.

21380356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1623 (or 1621 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21380356 is about 4623.8897045669. The cubic root of 21380356 is about 277.5481333058.

Adding to 21380356 its reverse (65308312), we get a palindrome (86688668).

It can be divided in two parts, 21380 and 356, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 21380356 in words is "twenty-one million, three hundred eighty thousand, three hundred fifty-six".