21779077887 has 18 divisors (see below), whose sum is σ = 35954697272. Its totient is φ = 12444518016.

The previous prime is 21779077819. The next prime is 21779077891. The reversal of 21779077887 is 78877097712.

It is not a de Polignac number, because 21779077887 - 2⁷ = 21779077759 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21779077897) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 1162063 + ... + 1180655.

Almost surely, 2^21779077887 is an apocalyptic number.

21779077887 is a deficient number, since it is larger than the sum of its proper divisors (14175619385).

21779077887 is an frugal number, since it uses more digits than its factorization.

21779077887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37199 (or 18603 counting only the distinct ones).

The product of its (nonzero) digits is 19361664, while the sum is 63.

Multiplying 21779077887 by its sum of digits (63), we get a square (1372081906881 = 1171359²).

21779077887 divided by its sum of digits (63) gives a square (345699649 = 18593²).

The spelling of 21779077887 in words is "twenty-one billion, seven hundred seventy-nine million, seventy-seven thousand, eight hundred eighty-seven".