21503764 has 6 divisors (see below), whose sum is σ = 37631594. Its totient is φ = 10751880.

The previous prime is 21503737. The next prime is 21503773. The reversal of 21503764 is 46730512.

It can be written as a sum of positive squares in only one way, i.e., 12250000 + 9253764 = 3500^2 + 3042^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2687967 + ... + 2687974.

Almost surely, 2^21503764 is an apocalyptic number.

It is an amenable number.

21503764 is a deficient number, since it is larger than the sum of its proper divisors (16127830).

21503764 is a wasteful number, since it uses less digits than its factorization.

21503764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5375945 (or 5375943 counting only the distinct ones).

The product of its (nonzero) digits is 5040, while the sum is 28.

The square root of 21503764 is about 4637.2151125433. The cubic root of 21503764 is about 278.0811142977.

The spelling of 21503764 in words is "twenty-one million, five hundred three thousand, seven hundred sixty-four".